Cryotherapy was used to treat 516 patients with various degrees of dysplasia and carcinoma in situ over a 7-year period. Seventy-one percent of patients had either severe dysplasia or carcinoma in situ. In 88% of the patients treated, a single treatment session was successful in eradicating the lesion. Treatment was defined as successful when cytologic and colposcopic findings were negative 1 year after treatment. Five percent of patients were lost to follow-up. The criteria for selection of patients and possible causes of treatment failure are discussed.