HIV infection affects dendritic cells (DCs) number, maturation, and function although the cause remains largely unknown. Purified CD34⁺ hematopoietic progenitor cells (HPCs) obtained from bone marrow of chronic HIV-infected patients were investigated for the differentiative capability toward mature DCs. HIV, although not in active replication, was found able to impair CD34⁺ HPC differentiation into mature DCs. These results suggest that DCs impairment found in HIV-infected patients may be related to a failure by bone marrow CD34 HPCs to produce an adequate number of DCs.