Since 1960, Mario's carryout has been a haven for the under-age offspring of affluent Bethesda homes looking for some exposure to a less stratified life, a taste of grit absent from bland suburban cafes and shopping malls.

In our Walt Whitman High School years, stuffy dates took my friends and me to Francisco's for pizza, where we ordered from leatherette menus and basked in the air of grown-up romance. But the hip guys tested our cool at Mario's, ordering pizza-to-go (dutch), and eating slices in the car.

These days, punks have replaced hippies, and would-be sophisticates have more Bethesda quiche cafes from which to choose. But at Mario's, nothing much has changed: The pizza still is legendary among a spectrum of customers that ranges from tattoos and T-shirts to the knife-creased uniforms of the dressed-for-success.

On a recent week night, a trio of construction workers huddled around one of the two tables in the back, brooding over the heat and bad air while downing Millers. A Gucci lawyer loaded a large pizza into his Mercedes convertible as a consultant in black skirt and heels awaited a sandwich.

"Two Italians!" the sandwich girl shouted above the sound of the evening news, and almost in the face of the young married who ordered a couple of subs. "Oh, sorry."

And a pizza clocked in at 18 minutes, from order to exit.

At first, recalls owner Mario Segreti, he gave away samples of his pizza to test his recipes and gauge customer reactions. Then, after he had won a steady following, River Road was widened and he was forced to move from his original location to the green diner that sits back a little from the road, where he currently presides. He was obliged to go out on the street and invite people to come back in because "they thought I'd gone high-class."

Now the word is that Mario's is scheduled to be razed. The shop will have a place in a new building on the site, but manager Al Abate predicts: "We'll probably lose a lot of regular customers. It will look a little too fancy for them."

Not to worry. Mario's has heart in place of pretense. It is clean, it is basic. A small pizza is $2.75. Like Mario, it is unadorned.

At 65, Mario plans never to retire. He is bulky, but not pizza-expert fat. There is a trace of an accent in his baritone (he sings at churches and used to play nightclubs, besides being a championship bowler). Beneath arching brows, his eyes dart to the door each time a customer enters.

Preparations for bacon-and-egg sandwich orders start the day at 6 a.m. Pizzas start rolling at 11, although requests for the house special--the Mariola, complete with sausage, pepperoni, mushroom, green pepper, onions, black olives, anchovies and extra cheese--don't begin until later. The pace picks up at lunch and continues until closing time at 10:30 p.m.

Mario likes to talk about the 400 kids who have worked for him over the years. He says that he has only fired "maybe five," and adds: "And every one, including those who were laid off, still come by to eat and bring their families."

Mario says that everyone in his household has worked here, "the wife, three sons, and the little one 10 years old will work here someday."

Square cardboard pizza boxes are stacked up to the ceiling next to a new addition: a PacMan machine. Three red stools along a narrow counter face a chart listing prices for singles, six-packs and cases of beer. Mario does not want to encourage the dining-in trade, explaining: "I don't want this to become a beer joint."

A chorus of video-game bleeps, a rattling air conditioner, ringing registers, and the sizzling sound of fries mingle with talk of numbers: "If I hadn't changed that five to a nine . . . . " Maryland State Lottery tickets are big business. And a "Hot Box" vending machine sells lucky numbers, on the order of a dream book, for those seeking lottery advice.

"Someone put in a quarter and hit when we first opened," recalls Abate. The customer won $500, word got around and, for awhile, the machine kept running out of tickets.

Over the years, Mario has perfected his sauce and crust as he learned his customers' tastes.

"I find it's 50-50 on the anchovies," he says. The crust he makes at home is slightly thicker than the one his public prefers.

"If I weren't so damn hard-headed about the way to cook pizza, I could do more business," he says, grasping the hand and arm of a visitor with both hands, for emphasis.

At Mario's the pizza takes at least 15 minutes, compared to the four advertised by a franchised competitor. The difference, Mario says, is that his are not cooked ahead and reheated.

And as he has for the last 20 years, he stays true to his personal philosophy, hewed from mountains of mozarella and parmesan and the unwavering loyalty of legions of customers.

"You have to have laws within yourself," he says, smiling and, perhaps because she came here as a teen-ager, he pinches the visitor's cheek goodbye.