One hundred fifty-two patients were enrolled in a study to evaluate 3 interferon (IFN) preparations used in combination with cryotherapy for treatment of anogenital warts. Subjects received subcutaneous injections (2 × 106units/m2) of IFN-αn1, -β, -γ or placebo 3 times a week for 6 weeks and cryotherapy with liquid nitrogen. Subjects were followed ⩽1 year. Among patients followed ⩾12 weeks, two-thirds had a complete response. No significant differences in rates of complete response (P =.37) or reappearance of a wart at the initial site (P =.20) were noted among the treatment groups. However, patients who received IFN-β or -γ developed new warts at a significantly lower frequency (P =.02). IFN administration was associated with side effects but was well tolerated. IFN-β was the least toxic of the 3 preparations and had the best therapeutic ratio. © 1995 by The University of Chicago.