Popcorn and unpopped toasted corn kernels on the dinner table? When the waiter at Rincon La Ronda restaurant in Quito, Ecuador (where the main attraction is the folkloric show), served these snack foods, I figured I had fallen into a real tourist trap.

But I had ordered seviche -- and that's what people in Ecuador eat with the salad of lemon-and-lime-marinated seafood. And after one taste, I understood why. The combination is traditional all over that Andean country because the crunchy nuttiness of the maiz tostal and the softer chewiness of the popcorn set off the marinated seafood dish marvelously.

By contrast, in Peru, its nominal birthplace, seviche goes with yuca, sweet potato and corn on the cob. In other Latin American countries, seviche keeps company with boiled potatoes, tomatoes, avocados, black or green olives, hard-cooked eggs, even goat cheese. One of the joys of seviche is its country-to-country differences and practically infinite variety of recipes (not to mention a variety of spellings -- ceviche, cebiche or seviche, all pronounced seh-VEE-chay). One of my keenest seviche memories is of eating it on the beach in Progresso, a seaside resort for locals on Mexico's Yucatan Peninsula. Progresso's restaurants specialize in seviche of tiny shrimp served in large ice-cream-sundae glasses (the ones we used to call frappe glasses) with sliced habanero chilies, chopped cilantro, garlic and onions, hot tomato salsa and perhaps even a little beach sand.

A small market under a bridge in Nassau, the Bahamas, produced another memorable seviche encounter. As I watched fishermen extract the conch from their shells, I was reminded a little of digging in the shells of escargot in French restaurants, except that instead of a morsel of meat, out comes a rather large creature. To be edible, the tough white flesh must be beaten into tenderness with a wooden mallet. After tossing the sliced raw conch with lime juice, tiny fiery hot red-bird chilies and sliced onion, the fisherman held out a paper plateful to the fascinated onlookers.

Seviche is commonly made of raw fish or raw conch, scallops and clams or of cooked shrimp, lobster, crabmeat, mussels, octopus and squid. For fish seviche, Mexicans favor sierra, a fish in the mackerel family. Spanish mackerel and kingfish have a similar oily quality. But I like a less oily fish such as grouper, striped bass, halibut, flounder, sole or other flatfish.

At the fish counter, I ask for "sushi-grade" fish -- in other words, absolutely fresh fish that is fit for eating raw. Because I buy only at stores with high-quality fish and a fast turnover, I feel pretty confident that the fish is safe to eat without heating it.

But not everyone feels equally comfortable about eating "uncooked" fish. Alison Swope, chef at Santa Fe East in Old Town Alexandria, says: "I've been afraid to put it on my menu because of people's perception of raw ingredients. It's one of those dishes that take a knowledgeable person to order it. It takes a person with a sophisticated palate and a history in travel."

Yet at Gabriel in the Barcelo Washington Hotel, on P Street NW, where seviche is on the tapas menu, chef Greggory Hill finds that "it's very popular, especially right now. Some people say, 'Oh, we wouldn't have that,' but when they try it, they like it."

All the brochures put out by the Food and Drug Administration caution at-risk people -- the very young, the very old and people with immune deficiencies -- against eating any raw animal products. And, FDA officials say, marination in acid, while it may break down the protein, will not kill any parasites contained in the fish.

"But," says Donald Kraemer, associate director of the FDA's Office of Seafood, "we don't want to scare people, either. There are raw products that have a long and honorable history, such as pickled herring."

As for sushi, the FDA's official position is a neutral one, with cautions mainly aimed at at-risk populations. But what lessens the risk factor in sushi fish can apply to seviche fish as well. As Kraemer points out, fish to be used in sushi is subjected to a specific regimen of commercial freezing -- a certain speed to a certain temperature that probably cannot be replicated at home. "The freezing regimen kills any parasites present," says Kraemer. The bottom line: If you want to prepare seviche without blanching the seafood first, do so with previously frozen products.

Marination can, according to the recipe, last from a half-hour to overnight. But "you have to be careful about soaking it too much," warns chef David Hagedorn of Trumpets, in Northwest Washington. "With overmarination, the proteins denature and it 'overcooks' to mushiness or becomes rubbery."

In his 1991 book, "The Art of South American Cooking," the late Felipe Rojas-Lombardi pointed out that "certain shellfish, such as shrimp and other crustaceans, in fact are not palatable when 'cooked' in lemon juice, for the process makes the flesh disintegrate. Shellfish," he wrote, "must be blanched first and then tossed in lemon or lime juice just long enough to flavor them. Crab, crayfish, prawns and lobster must also be blanched and just briefly tossed in juice. The same is true for octopus, squid and mussels."

Jeffrey Tomchek, chef at Old Angler's Inn in Potomac, puts the case more bluntly. Using scallops as his example, he says, "after six hours they are medium cooked, after 12 hours they're well done, and eventually they get smaller and harder until you have something resembling lead shot."

Rojas-Lombardi's book suggested that, after blanching, shellfish should be marinated only 10 minutes, adding, "To limit the amount of acid that comes into contact with these types of seafood, they are coated with oil first. The oil prevents acid burn and discoloration."

The acid in the marinade can be lemon or lime or a mixture of the two. Lemon imparts a truly tart flavor while lime is softer and more fragrant. Chef Hagedorn also uses sherry or balsamic vinegar -- vinegars with a little sweetness -- mixed with lime juice for a "balance of flavors," and he sometimes uses orange-juice concentrate without diluting it. In "Feasts of Life," Mexican cooking teacher Patricia Quintana also mentions "white" seviche, made with vinegar and juice of bitter oranges.

She also describes a cousin of seviche, which she calls "soused fish." Better known as escabeche, it seems to be preferred in hot climates because the fish is cooked, lasts, when refrigerated, for a few days and may be eaten hot or cold. Rojas-Lombardi explained that the "original purpose" of escabeche "was to preserve food with vinegar" and said it can be done with fish, shrimp, chicken, duck, turkey, artichokes and eggs.

The recipes below illustrate the diversity of seviche preparations; all but the first are prepared using blanched fish.

SAIGONNAIS SCALLOP SEVICHE

(6 to 8 servings)

This Asian-style seviche, a special-order appetizer at Saigonnais in Adams-Morgan, is a dish chef-owner Tin Quan learned to cook from his mother during his childhood in Vietnam. The original dish is made with fish, but Quan prefers the sweet flavor of scallops. People in at-risk groups should first blanch the scallops.

FOR THE SEVICHE:

3 pounds bay or small sea scallops

3/4 cup fresh lemon juice

1 teaspoon oil

1/4 cup chopped shallots

3 1/2 tablespoons fish sauce (nuoc mam)*

6 tablespoons sugar

3 ounces fresh rau ram (an aromatic leaf), sliced hair-thin*

3 ounces fresh basil, sliced hair-thin

3 tablespoons fresh ginger, sliced hair-thin

1/3 cup ground unsalted dry-roasted peanuts

1 teaspoon chili paste*

FOR THE GARNISH:

Oil for deep frying

1/4 pound prawn crackers*

Lettuce leaves

Place scallops in a non-corrosive bowl and marinate in lemon juice for 1/2 hour. Drain scallops in a strainer over a bowl in the refrigerator for 2 hours. Dry completely with paper towels.

Heat oil in a nonstick skillet, add shallots and saute until browned. Blend fish sauce with sugar until sugar is completely dissolved. Pour over scallops and add rau ram, basil, ginger, peanuts, chili paste and fried shallots. Mix well and refrigerate until ready to serve.

Heat oil in a saucepan, add prawn crackers, one or two at a time, and fry until puffed, about 10 seconds. Line a serving dish with lettuce leaves and pour scallops over top. Arrange fried prawn crackers around edges of dish.

* Available at Asian grocery stores.

Per serving without garnish: 283 calories, 42 gm protein, 14 gm carbohydrates, 7 gm fat, 1 gm saturated fat, 76 mg cholesterol, 673 mg sodium

OLD ANGLER'S INN SANTA FE SHRIMP SEVICHE

(4 servings)

1/2 pound rock shrimp, peeled and deveined

1 tablespoon olive oil

2 cups Clamato juice

1 tablespoon Worcestershire sauce

1 ripe avocado, peeled, pitted and diced

1/4 bunch cilantro, minced

1/4 cup minced red onion

1 Anaheim chili, roasted, peeled, seeded and minced

Juice of 1 lime

Salt and white pepper to taste

Ground cumin to taste

Lime wedges, cilantro sprigs and blue corn tortilla chips, for garnish

Boil shrimp in water to cover until just done. Do not overcook. Rinse under very cold water and drain. Combine shrimp with oil, Clamato juice, Worcestershire sauce, avocado, cilantro, onion, chili, lime juice, salt, pepper and cumin. Garnish with wedges of lime and sprigs of cilantro. Serve with tortilla chips.

Per serving: 215 calories, 15 gm protein, 13 gm carbohydrates, 13 gm fat, 2 gm saturated fat, 111 mg cholesterol, 879 mg sodium

ROOF TERRACE RESTAURANT CARIBBEAN SEAFOOD ESCABECHE

(6 servings)

For this Kennedy Center restaurant special, executive chef Max-Philippe Knoepfel chooses fish that are always readily available. He says: "I like to serve the seafood escabeche on a bed of cold, finely shredded lettuce. The best variety for this purpose is iceberg, which has no real flavor but does have refreshing crunchiness."

1/2 cup olive oil

1/2 pound red snapper fillet

1/2 pound halibut fillet

1/2 pound boneless, skinless tuna steak

3 garlic cloves, peeled and chopped

1 to 2 dried red chilies, optional

1 bay leaf

1/2 teaspoon Spanish paprika

1 1/2 cups red- or white-wine vinegar

1 sprig fresh rosemary or 3 to 4 sprigs fresh thyme

1/2 teaspoon coarse salt

2 tablespoons coarsely chopped Italian parsley or cilantro

1 ear corn, cooked and sliced into rings

1/8 pound feta cheese, cut into cubes

6 alfonso or Kalamata olives

1 lime, sliced

Heat oil in an 8-inch skillet. Add fish a few pieces at a time and quickly toss over high heat to sear, about 1 to 2 minutes. When fish is cooked, transfer pieces with a slotted spoon to a deep serving dish.

To the same skillet, add garlic, hot chili and bay leaf. Saute over medium heat until garlic is barely golden. Quickly add paprika and vinegar. Stir and bring to a boil over medium-high heat. Reduce heat and add rosemary and salt. Simmer gently 5 to 10 minutes, stirring occasionally. Cool about 20 minutes undisturbed. Pour while still warm over fish. Let cool to room temperature. Toss in parsley and garnish with rounds of corn, feta, olives and lime slices. Serve immediately or refrigerate up to 3 days.

Per serving: 337 calories, 26 gm protein, 9 gm carbohydrates, 23 gm fat, 4 gm saturated fat, 52 mg cholesterol, 362 mg sodium

MUSSEL SEVICHE

(10 servings)

In "The Art of South American Cooking" (HarperCollins, 1991), the late Felipe Rojas-Lombardi has an entire chapter on seviche. He suggests making it with tuna and fresh ginger; flounder with corn, sweet potatoes and alfonso or Kalamata olives; swordfish with bell peppers; cooked shrimp with celery, carrots and bell peppers; raw clams with potatoes; scallops, squid and octopus; duck; and mushrooms.

5 pounds very fresh black or green mussels

1/2 cup plus 2 tablespoons olive oil

1/2 cup dry white wine

4 sprigs fresh thyme or 1 teaspoon dried thyme

3 large new potatoes, washed, cooked and cut into 1/2-inch cubes

1 1/2 pounds tomatoes, cut into 1/2-inch cubes

1/2 small sweet onion, peeled and thinly sliced

4 tablespoons fresh or frozen green peas

1/3 cup fresh lemon juice

1 teaspoon coarse salt

1/3 cup chopped fresh Italian parsley

Clean mussels. In a dutch oven with a tight-fitting lid, combine the 2 tablespoons of olive oil, 2 tablespoons of the wine, thyme and mussels. Cover and steam over high heat until mussels are barely open, 5 to 8 minutes. Discard any mussels that have not opened. Let juices in pan stand for a few minutes so sediment settles to bottom. Strain into a bowl through a sieve lined with a double layer of cheesecloth.

Using a paring knife, detach mussels from their shells, being careful not to tear them. Place in the bowl with the mussel juices. Add potatoes, tomatoes, onion, peas, lemon juice, salt, parsley and remaining oil and wine. Toss gently. Serve at room temperature.

Per serving: 364 calories, 29 gm protein, 22 gm carbohydrates, 16 gm fat, 2 gm saturated fat, 63 mg cholesterol, 872 mg sodium

LOBSTER SEVICHE

(8 servings)

"Chefs in popular tourist cities compete with one another to create tastier renditions of traditional recipes," says Patricia Quintana in "The Taste of Mexico" (Stewart, Tabori & Chang, 1986). This lobster version comes from a hotel in Acapulco.

FOR THE LOBSTER:

Salt to taste

6 lobster tails

FOR THE MARINADE:

2 quarts fresh orange juice

1/2 cup fresh lime juice

1/3 cup tequila

1/2 cup chives, finely chopped

Salt to taste

FOR THE GARNISH:

2 tablespoons chopped chives

Sesame bread sticks

To prepare lobster, bring 2 to 3 quarts of water and salt to a boil in a saucepan. Add lobster tails and boil for 15 minutes. Cool slightly in cooking water, remove and shell tails. Shred meat.

Combine orange and lime juices, tequila, chives and salt. Pour over lobster and refrigerate 2 hours. To serve, spoon seviche into individual bowls and garnish with chives. Serve with sesame bread sticks.

Per serving: 205 calories, 35 gm protein, 10 gm carbohydrates, 1 gm fat, trace saturated fat, 121 mg cholesterol, 770 mg sodium