One hundred and sixty five heterosexual men and women with genital warts were treated with inosine pranobex (Imunovir) or conventional treatment, or both. Inosine pranobex was found to be more effective in lesions of longer duration, whereas conventional treatment was more effective in genital warts of a shorter duration. Supplementation of conventional treatment with inosine pranobex increased the success rate from 41% to 94%. Immunological studies in 134 patients with genital warts showed an increased number of B cells in 21% of peripheral blood samples. Absence of major defects among circulating lymphocytes suggested that patients with genital warts may have a local immune reaction.