In addition to the well known T-cell dysfunctions in AIDS, hypergammaglobulinaemia and autoimmune phenomena indicate an involvement of the B cell as well. Reports of HTLV-III/LAV-infected B cells suggest T-cell-independent B-cell abnormalities. To look for early B-cell dysfunctions, we examined a high-risk group of AIDS consisting of six homosexuals with PGL and HTLV-III/LAV antibodies, comparing these data to those of patients with AIDS/ARC and a normal control. In vitro studies included the B-cell proliferation response (3H-thymidine uptake) to Staphylococcus aureus Cowan I and the differentiation response (Ig secretion into culture supernatants) to T-cell-dependent/-independent polyclonal B-cell activators (PBAs). Profound alterations were found in both the proliferation and the differentiation responses. The weak response even to T-cell-independent PBAs indicates a B-cell dysfunction that is not due only to a T-cell defect in patients with PGL, similar to that observed in AIDS.