Sexually transmitted diseases caused by human papilloma viruses, such as condylomata acuminata, are increasing in incidence and are often difficult to treat because of their tendency to recur. Many reports in the literature document the usefulness of interferons topically or systemically in these diseases. A randomized study was conducted to evaluate interferon Alfa-2b (Intron A) as adjuvant therapy following CO2 laser surgery of condylomata acuminata. A low-dose regimen was administered (two courses with 1 million I.U. s.c. daily for 6 days with a 2-week interval between the courses) and had hardly any side-effects. The recurrence rate in the therapy group was significantly reduced (42% vs 81%), so routine prophylaxis of recurrence with interferons in condylomata acuminata should be discussed.