Blues in the Night. Musical entertainment starring Leslie Uggams, Jean Du Shon, Debbie Shapiro. Conceived and directed by Sheldon Epps.

It would be pleasant to be able to cheer the occasion that brings svelte and versatile Leslie Uggams back to Broadway for the first time since ''Hallelujah, Baby'' in 1967. Unfortunately, ''Blues in the Night,'' costarring Miss Uggams with Jean Du Shon and Debbie Shapiro, gives scant cause for cheering. The musical anthology at the Rialto Theater is doubly exploitative. It exploits the talents of its principal performing trio. And it exploits the role of woman as sex object, whether for tearfully sentimental or vulgarly comic purposes.

The program, ''conceived and directed'' by Sheldon Epps, ranges through some two dozen numbers, from standards like ''These Foolish Things Remind Me of You'' and ''Willow Weep for Me'' to works by Bessie Smith and other black writer-performers. The Rialto threesome brings strong vocal resources to the material at hand, though both Miss Uggams and Miss Shapiro seem stylistically miscast on occasion. Pianist-conductor Charles Coleman, the only man in the company, periodically doubles as vocalist.

''Blues in the Night'' ultimately succumbs to the monotony of its treatment, the dreariness of its period setting (a cross-section of a tawdry Chicago hotel in 1938), and a lack of imagination in the staging. Adding to the belittling anonymity of the treatment, the cast members are identified only as Woman No. 1, 2, 3 respectively. Even when they share a song, the performers betray no awareness of each other's presence.

The effect is isolatingly impersonal. Near the very end of the evening, as they join voices for ''I Gotta Right to Sing the Blues,'' a sympathetic spectator can appreciate their lament.