ABOUT THIS TIME of year -- Mardi Gras is Tuesday, if you haven't noticed -- a lot of people get the urge to eat Cajun or Creole food, only they're not always sure just which cuisine is which. Which is understandable since, thanks to star chefs such as Paul Prudhomme and Emeril Lagasse, the two are more and more often lumped together as "New Orleans" cuisine. So broad are some "creole" dishes, in fact, incorporating Caribbean and Gulf Coast flavorings, that they might as well be called Nouvelle Orleans.

The good news is, both Cajun and Creole restaurants in the Washington area are likely to offer you at least a little of each. Even so, it's worth thinking through the differences in the cuisines, because they reflect two different though indivisible cultures and evoke two rich histories.

To put it bluntly, Creole food was the cuisine of the wealthy, the urbanites, while Cajun was the home cooking of the slaves, the servants, the backwoods and bayou dwellers. This in turn leads to another distinction: Cajun food is apt to be less expensive than Creole (or, nowadays, transformed into appetizers), served in less formal establishments and consumed more often with beer than with liquor or wine.

The names themselves are the first clue: Creoles were French or Spanish citizens born, usually of aristocratic families, in Louisiana, and aside from a few political disputes, the French felt socially right at home with the rich Spanish they replaced -- and whose European-trained chefs they often adopted. (Eventually, under the elaborate caste system devised for mixed black-French or French-Indian offspring, "Creole" was also applied to those with upper-class connections, but they were virtually French in language and custom.) Hence Creole food is at heart European, and court or "city" European at that, heavy on the cream-based sauces, prepared in distinct "courses" in the continental style, and involving a variety of cooking utensils and methods.

"Cajun" comes from "Acadian," the rural southern-French settlers of Nova Scotia, who were forced to emigrate to the last great French territory when Canada fell to the British in the early 18th century. At the end of their long exodus, retold in Longfellow's "Evangeline," few had any possessions left at all and were forced to live off the land (and make allies of the other non-Europeans). Consequently, Cajun food is a much more "American" invention, a haphazard amalgam of country French, African, coastal Mexican, Spanish and indigenous Choctaw and other Indian ingredients and techniques. There are many more one-pot dishes and finger foods than in the Creole repertoire because Cajun kitchens were more sketchily equipped and because poorer, tougher ingredients required longer cooking.

Creole tables were set with risen breads, coffee and sweets (sugar, Caribbean plantation coffee and white flour all being fairly expensive). Cajun cooks relied on skillet breads and fried doughs. Cream sauces, butter and cheese are prominent in Creole recipes -- hard to imagine Creole brunch without hollandaise sauce -- but relatively rare ingredients in Cajun, because there were far fewer Cajun families with either the land or grain-money to raise cattle.

Creole food is generally seasoned with traditional green herbs, Dijon mustard and so on; the sauces, thickened in the European fashion with butter and flour, are frequently added toward the end of the cooking process.

Cajun food is usually thickened with roux (literally, "red," flour browned in oil or grease) or vegetable thickeners, notably South American okra and North American sassafras file) and seasoned throughout the process with the various chilies and pepper sauces that are also all-American. Cajun cooks also tended to serve more corn, particularly in the form of cornmeal and hominy, and took quickly to the Caribbean barbecue. The so-called "holy trinity" of Cajun cooking -- bell peppers, celery and onions -- were cheap fillers and are used much more generously than in Creole recipes. Cajuns also have a second trinity, the "three peppers" -- black, white and Tabasco -- whence cometh the "blackening" now standard in even non-New Orleans grills.

Both Cajun and Creole cooks, of course, enjoyed the shellfish and wild game available in the region. However -- although this is rapidly changing -- Cajun food is traditionally far more reliant on bayou (freshwater) and cheaper sources of protein: alligator, "trash" fish like the now famous redfish, squirrel, turtle, chicken, shellfish and pork rather than the veal, beef and lamb featured in haute Creole cookbooks. Most Cajun staples such as jambalaya (probably from the French "jambon" for ham and African "ya" for rice), gumbo (from a West African word for okra) and "dirty rice" (so-called because it is colored by chicken livers, cracklin's or the like) were ways of stretching cheap rice and vegetables. Modern versions, along with those trendy "pasta ya-yas" combining sausage, chicken, shrimp and so on, are highly exaggerated versions of the original big-pots-o'-leftovers.

If you're cholesterol- or calorie-conscious, incidentally, you might note that either can pack a wallop: Cajun "fat" comes primarily in the form of meat grease and oils, while Creole fat is generally butter. Cajuns fry, Creoles saute.

At Louisiana Express, a chummy, crowded semi-carryout in Bethesda, the mostly-Cajun menu is divided into categories -- tomato-y creoles, roux-thick etouffes, jambalayas and stir-fries -- and is available with a progression of ingredients such as chicken, spicy andouille sausage, crawfish and shrimp. It makes great fish beignets (fritters) but gets a little cute with the revisionist "creole pizza."

Carmella Kitty's is pretty much what you'd expect from a Louisiana Express clone upscaled in the post-Prudhomme era into a Dupont Circle town house. The catfish beignets come with tomato-corn relish, the crawfish turn up inside Cajun "potstickers," the andouille sausage is tossed over gnocchi with gruyere cheese, etc.

The Copeland's franchises in Alexandria and Rockville offer hefty Cajun- and Creole-flavored pastas, blackened and creole'd seafoods and the requisite bit of barbecuing with trendy spellings ("alfredeaux" sauce, monterey jacques cheese, etc.). Lulu's, the Auger family's imitation Bourbon Street, has an ambitious menu of etouffes and jambalayas, though a better bet is the bacon-wrapped and crab-stuffed shrimp that is hot in both Charleston, S.C., and New Orleans.

Crescent City in Alexandria mixes its cuisines -- deep-frying catfish in cornmeal and then topping it with "creole sauce"; serving a "pasta gris-gris," referring to the voodoo charm, that combines a cream sauce and nouvelle black pepper pasta with tasso ham, andouille sausage and chicken; and topping a "cajun-spiced fettucine" with barbecue sauce and shrimp.

B. Smith's nominal frontwoman, former model Barbara Smith, is a longtime New Yorker, but she's descended from a sturdy Southern family (her mother's recipes were at the heart of the original Manhattan menu); and the executive chef, Rupert Holmes, spent 14 years at Prudhomme's iconic K-Paul's in New Orleans, Holy See of the blackened redfish movement. As a result, a number of Holmes's additions have a Nouvelle Cajun flavor: crawfish in the seafood pasta, black pepper in the brioche, deep-fried okra and Vidalia onion rings with "Tabasco mayo," candied yams with the fois gras, hoppin' john, red beans and rice with corn bread and so forth.

("Hoppin' John," incidentally, is a whole book in itself -- and a whole bookstore, and its owner, in Charleston -- and one of these days it and its relatives will be a column as well. Watch this space.) There are a number of other spots -- Two Nineteen, Cajun Bangkok and the various R.T.'s branches, all in Alexandria -- that also offer Cajun and/or Creole dishes. Tornado Alley, the Wheaton nightclub with the blues attitude, has a short menu that includes crawfish and andouille etouffes, fried catfish po' boy and is testing some new "zydeco pizzas" with barbecue, jalapenos, shrimp and andouille. (Is this a trend?) They'll be available Friday, Sunday and Fat Tuesday.

And if there's ever baseball in Baltimore again, remember that the classy little brewpub Sisson's by the Cross Street Market also has a New Orleans slant on life, including seafood creole with andouille-dirty rice, shrimp etouffe, blackened redfish and smoked crayfish cakes. B. SMITH'S -- 50 Massachusetts Ave. NE (Union Station), 202/289-6188. Business/informal; entrees $10-$20. Wheelchair accessible. CARMELLA KITTY'S -- 1602 17th St. NW; 202/667-5937. Not wheelchair accessible. COPELAND'S -- 1584 Rockville Pike, Rockville, 301/230-0968 and 4300 King St., Alexandria, 703/671-7997. Business/casual; entrees $6-$15.75. Wheelchair accessible. CRESCENT CITY -- 1120 King St., Alexandria, 703/684-9505. Informal; entrees $9-$16. Wheelchair accessible. LOUISIANA EXPRESS -- 4921 Bethesda Ave., Bethesda, 301/652-6945. Casual, entrees $2.75-$12. Not accessible. LULU'S -- 22nd and M Streets NW, 202/861-5858. Casual; entrees $6.25-$15. Wheelchair accessible.