Peripheral blood mononuclear cells were obtained from 20 untreated condyloma acuminatum patients and from an equal number of sex- and age-matched controls and assayed for cell surface antigen expression, natural killer activity, and lymphokine production. Patient peripheral blood mononuclear cells had significantly lower helper-to-suppressor T-cell ratios (Leu3/Leu2) (p<0.05) and significantly higher percentages of Leu 2+ Tac+ cells (activated suppressor/cytotoxic cells) (P<0.05) and Leu 2+ OKM1+ cells (suppressor cells) (P<0.01). Natural killer activity of condyloma acuminatum patients was significantly lower (P<0.05) than that of controls. Production of interleukin-2 and interferon gamma, but not interferon alpha, was significantly (P<0.01) decreased in condyloma acuminatum patients. There was an inverse correlation between the in vitro production of interleukin-2 and interferon gamma and the percentage of Leu 2+ OKM1+ cells (suppressor) (P<0.01). Thus, patients with condyloma acuminatum differ from controls by demonstrating (1) decreased natural killer-cell activity, (2) decreased production of lymphokines which enhance natural killer-cell activity (i.e., interferon gamma and interleukin-2), and (3) an increased proportion of T cells with a suppressor phenotype. © 1987 Plenum Publishing Corporation.