Early depletion of CD34⁺ progenitor cells and CFU-C is a feature of both a primary isolate and a T-tropic molecular clone of HIV-1. Thy/Liv grafts were infected with either NL4-3 or HIV-1 strain JD, as described in the Materials and Methods. Data (mean ± SEM) summarize two experiments with animals from two donors, with 21 animals at day 12 and 21 animals at day 28. †.1 >P > .05 and *P < .05 for difference between value and total thymocytes (unpaired t-test). (□) Total; (▨) CFU-C; (▪) CD34⁺.