To determine the value of combining interferon with standard local therapy in the treatment of human papillomavirus infection, 97 patients with anogenital warts were randomized to a short course of either interferon plus podophyllin or podophyllin alone. Interferon alpha 2b (1.5 x 10(6) IU) was injected intralesionally and podophyllin resin applied topically to each of three warts once weekly for 3 weeks. Maximal responses occurred within 2 weeks of therapy, and overall there was complete clearance of treated warts in 67% of interferon and podophyllin versus 42% of podophyllin recipients (P less than .05, chi 2). Clearance rates were greater in women, patients with warts of less than or equal to 12 months' duration, and HIV-seronegative patients. Of patients with complete clearance, 67% of interferon and podophyllin and 65% of podophyllin recipients experienced recurrences. Thus, in short treatment courses of anogenital warts, intralesional interferon enhanced the effect of topical podophyllin, and trials of combination therapy using more intensive or prolonged regimens of interferon are warranted.