Animated trio of one-acters -- and some not-so-private lives; Win/Lose/Draw. Three plays by Mary Gallagher and Ara Watson. Starring Lynn Milgrim and Christine Estabrook. Directed by Amy Saltz.

Two accomplished actresses giving adroit performances in three short plays provide the principal pleasures of ''Win/Lose/Draw,'' at the Provincetown Playhouse. This is not to imply that authors Mary Gallagher and Ara Watson have neglected to provide the where-withal for vivid stage characterization. It is rather to applaud Lynn Milgrim and Christine Estabrook for the artistry with which they animate the Gallagher-Watson sketches under Amy Saltz's sure-handed direction.

In ''Little Miss Fresno,'' the actresses register the reactions of a pair of anxious mothers waiting to see whether their small daughters will make the finals of a beauty contest for tots. Miss Estabrook plays a seasoned veteran of these ghastly rites, while Miss Milgrim is the timid newcomer.

Miss Watson's ''Final Placement'' casts Miss Milgrim as a social worker attempting to combine professional detachment with compassion as she deals with a distraught, child-abusing welfare mother (Miss Estabrook) whose little son has been removed from her custody and is nearing adoption. With its relevance to one of the most tragic social and familial problems of the times, this is also the most dramatically effective of the three pieces.

Finally, Miss Gallagher's ''Chocolate Cake'' teams its starring duo as a tough city mouse and a naive country mouse who meet at a conference in a western Massachusetts motel and share confidences. It is funny up to the point at which Miss Gallagher, like the couple in the Comden-Green song, gets carried away.

Wearing a series of suitable wigs, Ruth Morley costumes, and makeups, the Misses Milgrim and Estabrook give a diverting demonstration of versatility at work. Louis Nelson designed the adaptable setting and David F. Segal lighted it.