Mauro V. Vincenti, a paragon of la cucina italiana in the United States and proprietor of two of its best-known outposts in Los Angeles, died of cancer on Wednesday at his Los Angeles home. He was 53.

Tirelessly passionate about the cooking of his native Italy, Mr. Vincenti championed the subject in Los Angeles for nearly two decades. He was the owner of the chic -- and very expensive -- Rex il Ristorante.

He opened it 15 years ago in downtown Los Angeles in a landmark Art Deco building he helped restore. The revamped 1928 building, sumptuously patterned after a 1930's Italian luxury liner, was the setting in the movie ''Pretty Woman'' where Richard Gere, playing a billionaire, took his impecunious made-over strumpet, Julia Roberts, by limousine.

Besides film makers, Mr. Vincenti's good taste and exquisite kitchen attracted stylish parties and weddings. A restaurant critic of The Los Angeles Times, S. Irene Virbila, just this month called Rex ''one the best Italian restaurants in the country,'' despite Mr. Vincenti's failing health and a precarious downtown location.

Not a chef himself, Mr. Vincenti went scouting for Italy's best, and he was always on the lookout for the very best prosciutto or olive oil as well as new items to put on the menu. He was a Roman by birth and originally intended to be a teacher of Italian literature, which helped explain his rich, scholarly knowledge of food, its history and the world food scene.

Before opening Rex, he operated other restaurants, first Mauro's in Glendale, Calif., and later Fennel and Pazzia in West Hollywood. Pazzia now is Alto Palato, a baby Rex as reasonably priced as Rex is famously pricey.

Ruth Reichl, restaurant critic for The New York Times, two years ago called Alto Palato the best bargain for dining out in Los Angeles. She described it as a roomy, elegant place where the spaghetti was al dente and the zucchini and the flavors ''understated and delicious with the true taste of Italy.''

Mr. Vincenti was born a stone's throw from the Trevi Fountain. He studied literature in college but moved to the United States and the West Coast in the mid-1970's, originally intending to go into the movie business.

He is survived by his wife, Maureen Murphy Vincenti, and two teen-aged sons by a previous marriage, Marco and Nicolas, both of Glendale.