A cohort of 341 symptomless anti-human immunodeficiency virus (HIV)-1 positive individuals was screened over a 6-year period to detect a serum monoclonal gammopathy (MG) and to approach the prognostic significance of such anomaly in HIV infection. Eleven individuals with a MG were followed-up over a mean period of 50 months from the date of discovery of the MG. At the end of this period, the MG had disappeared in seven individuals, was still present in the four others. The appearance of a second MG was noticed in two cases, and of a third in one case. Immunoglobulin (Ig) typing identified eleven IgG kappa and three IgG lambda. Mean serum concentration of MG of individuals with persistent MG (14.3 g/l) and of individuals without (4.2 g/l) was significantly different (P < 0.05). The discovery of a MG was without prognosis value on the disease progression and did not appear as a primary event in the subsequent development of lymphoma.