Highly purified (>98%) CD34(+) cells directly after isolation (D-0) or 2 weeks in culture (D-14) were CD4(+) and contained mRNA for the T-tropic HIV coreceptor, CXCR-4, and minor co-receptor, CCR-2B. D-14 but not D-0 cells were RT-PCR positive for mRNA for the major M-tropic human immunodeficiency virus (HIV) co-receptor, CCR-5, and potential coreceptor, CCR-1, D-14 and D-0 cells were susceptible to T- (HXB2) and M-tropic HIV (Bal), showing greater virus production with Bal than HXB2, and with higher virus production levels in D-14 compared to D-0 cells. Seven days post-infection of D-0 cells Bal DNA was present in CD14(bright) and CD14(-) fractions, suggesting D-0 infection of diverse progenitor types. HXB2 DNA was detected in CD14(bright) cells alone indicating D-0 infection of monocyte progenitors only, It is concluded that CD34(+) cells and cultured derivatives are susceptible to M- and T-tropic HIV and this correlates in part with co-receptor expression at the mRNA level.