Though the Alvin Ailey American Dance Theater has been ensconced in the Kennedy Center Opera House since Tuesday evening, in a sense the company's engagement seemed really to have begun last night. For the first time, the dancers had the kind of magnetic grip on their material -- and the audience -- that they have accustomed us to in so many past seasons. The payoff was a bountifully rewarding theatrical experience.

A number of obvious factors figured in the rejuvenation: a revitalized ensemble, once again excitingly true in line and rhythm; the warmth and prodigious presence of Judith Jamison, appearing for the first time during this run; and Ailey's own choreography, some of the sturdiest examples of which formed the bulk of last night's program.

A further sign of the rehabilitation was the performance of Ailey's masterpiece "Revelations," which was not only vastly improved over opening night, but also came closer to the original spiritual fire of the work than many another account of recent years. Though unannounced in the program, Jamison took her usual place in the first two movements, her undulant jubilation spreading an effusive glow all around her. Every section of the work seemed reborn in the flush of the evening's sustained vibrancy. Much neater diction, pitch and balance in the accompanying choral singing also helped.

The evening began with Ailey's "Streams," an "abstract" piece in a vein that reminds one far more of his early training with Horton, Graham and Holm than of his more customary jazz idioms. It would be twice as effective at half the length, but it's still an impressive display of muscular and spatial logic and taut performance showed off its best qualities.

Of Judith Jamison's performance in "Cry," Ailey's brilliant, impassioned solo for her on the theme of black womanhood, little needs to be said to confirm past praise except that she was in particularly radiant form.

The local premiere of Margo Sappington's "Medusa" was, in this context, a decided anticlimax. The legend is treated as a frieze come-to-life in slithery, reptilian movement -- the choreography is strong on atmosphere and eroticism, but weak in structural economy and taste.