When you watch the new TV production of A Raisin in the Sun on Monday — and you should — you're not just watching an ensemble of marvelous actors in a heart-touching play. You're also watching history.

The play by Lorraine Hansberry was a revelation when it landed on Broadway in 1959. It was not only ''an unexpected hit,'' as theater critic Howard Taubman later wrote. It was an African-American woman's portrayal of ordinary lives and longing. Taubman noted that, up to that time, such lives were ''long either a subject of indifference or, at best, the concern of self-conscious white writers.'' As theater historians Richard Eyre and Nicholas Wright said, the play described ''a world of which most of its audience were ignorant.''

The same can be said today, in some ways, because the play is so very much a part of a different time and attitudes. But it is rich in issues that still can be felt — and which in many cases cross racial lines. Issues about the nature of success, about generational conflict, about the culture of the past bumping into the seductions of the contemporary.

It is, in other words, a remarkable work and one that makes the premature loss of Hansberry — who died in 1965 at the age of 34 — all the more painful. But the play has survived. The original Broadway cast, including Sidney Poitier and Cleveland's Ruby Dee, starred in a 1961 movie version. A sturdy television production aired in 1989. Stage revivials include a Broadway production in 2004 that was widely acclaimed and awarded. Most of the cast, and the director, of that production have come together for the new TV version.

Airing at 8 p.m. Monday on ABC, the three-hour (including commercials) presentation finds the Younger family of Chicago at a pivotal point. The family patriarch has died, leaving behind a $10,000 insurance policy. His widow, Lena (Phylicia Rashad), must decide how to put that money
to use. Should it help her daughter, Beneatha (Sanaa Lathan), go to medical school? What about Lena's son, Walter (Sean ''Diddy'' Combs), who has dreams of being more than a chauffeur — and dreams of a better life for his wife (Audra McDonald) and son (Justin Martin)?

All of them live in a small apartment in a bad neighborhood. But when Lena decides to buy a house, she runs up against Walter's pent-up emotion as well as a white neighborhood association that does not see the Youngers as ideal neighbors. (John Stamos appears briefly as the representative of the association.)

While that provides the framework for the play, its power lies in the characters' everyday thoughts and aspirations. Beneatha is especially pivotal, as she is pulled between the middle-class attitudes of one suitor (Sean Patrick Thomas) and the seemingly exotic life offered by another (David Oyelowo).

The most solidly built characters in the play are Lena and her daughter-in-law Ruth, and some of the best moments involve the interplay between Rashad and McDonald. But even they are subject to outside forces, especially pressure from Walter.

Which brings us to Combs' performance. His appearance in the Broadway play was sometimes interpreted as a way to bring a younger audience to the theater, and there's no doubt some of that thinking is at work here, too. Certainly ABC has run ads presenting Combs more prominently than he is in the actual production, in which Rashad, McDonald and Lathan all take center stage for stretches.

But Combs is quite capable, especially when it comes to the quiet burning within Walter. This is a departure from Poitier's performance in the 1961 film, which was more frenetic, a mix of last-ditch desperation and unsatisfied hunger. Combs' Walter is more beaten down, and his rage all the more effective when it breaks through. (The play's title comes from a Langston Hughes poem, A Dream Deferred, which asks whether such a dream dries up ''like a raisin in the sun . . . or does it explode?'') And he pulls off Walter's transition from an adolescent mind-set to real manhood.

Still, as good as he can be, Combs is eclipsed by other performances, especially Rashad. But all the actors are working with fine material. Paris Qualles' adaptation of the Hansberry play does make some unnecessary concessions to screen life, particularly when it tries to show us the characters' activities outside that cramped little apartment. But as it goes along, director Kenny Leon pulls us ever more tightly into their world, and their hearts.