The Viet Nam Inn, just two months old, has not yet been discovered by many non-Vietnamese in the city. It should be discovered.

It is a small restaurant, hidden away in Clarendon across from the Arlington Courthouse. Families might be tempted to pass it by because of the dim lighting and a bar that dominates the right side of the room. But inside we felt welcome - even after our two-year-old went on a rice-flinging spree with my husband's chopsticks and then bumped his soft drink into the booth.

The drink was graciously mopped up by Hai Nguyen, a State Department worker for 20 years who fled Vietnam when the Communists took over. He and his wife, Linda, together with Binh Tran, a former Vietnamese navy officer, and his wife, own the restaurant, wait tables, mix drinks, clean up and provide a friendly, comfortable atmosphere. Ly Ho, a relative of the Trans, prepared the food according to "secret recipes" that Nguyen himself claims not to know.

Whatever her secrets, the food was some of the best Vietnamese we have eaten in the Washington area. The menu offered a range of dishes mainly from the Can Tho province, about 150 miles south of Saigon, and a few Chinese dishes. The most expensive entree is shrimp grilled on sugar cane for $5.50 - Nguyen says their shrimp is what they are noted for. Most dishes were in the $2.50 to $3.50 range. All food is prepared when ordered.

We arrived about 6 p.m. on a Saturday night. Only one other family was dining. Although Viet Nam Inn has not yet geared up for the smaller set - there are no high chairs, boosters or even telephone books available - we were able to keep our son entertained during the short wait by pretending the folded napkin was a red ghost.

My husband ordered the wonton soup (70 cents), a spicier version than its Chinese cousin, and better, he thought. I ordered the three-course dinner ($5.50), which came with a traditional Vietnamese soup - asparagus with crab meat. It was thick and good, with chunks of crabmeat and fresh asparagus. The waitress also brought our son a free dish of asparagus soup. (Nguyen said later that although no children's portions are available at a reduced rate, it is a policy to provide free side dishes for the children.)

Next came the appetizers, imperial roast pork rolls ($1.95) for my husband, and imperial rolls (or spring rolls as they are known elsewhere) for me. The pork rolls are cold and a strikingly pretty dish.

Ground pork, carrots, onions and cellophane noodles are wrapped so that the green vegetables show through the translucent white rice paper. They are dipped in a clear sweet and sour sauce at the table. My husband thought they were delicious.

My rolls were similar, only deep fried in an excellent crisp and flaky pastry.

For a main dish my husband chose the pork sauteed with vegetable ($3.50), which he thought was well-prepared with a delicate sauce. My beef grilled on stick was outstanding. The beef is marinated in a sauce of sesame seeds, scallions, garlic, sugar and soy sauce, then sprinkled with peanuts and grilled.

Fried rice came with both dishes; it was the only disappointment of the meal. it tasted a little of fish oil and the vegetables were canned. The jasmine tea did make up for it, though. The dessert was lychees and longan (both 65 cents) which we all enjoyed.

Families with children with are little older should find no problems with the service, which is very friendly. And the prices are particularly attractive: our bill came to $13.48 plus tip.

Hour: 1 a.m. to 10 p.m. every day except Sunday. No credit cards, but personal checks are accepted.