Human parvovirus 4 (PARV4) is a recently discovered member of the Parvoviridae. We investigated the presence of this virus in bone-marrow aspirates of 35 Italian patients with AIDS. Viral DNA was detected by polymerase chain reaction in over 40% of patients (16/35). The infection was most prevalent in injection drug users (IDU; 12/18; 66.7%) as opposed to non-IDU (4/17; 23.5%). PARV4 infection is widespread in Italian patients with AIDS.