A study undertaken to assess the reliability and effectiveness of cryosurgery in cervical intra-epithelial neoplasia is described. During 1 5-year period a total of 416 patients were so treated and the records were studied retrospectively. This study demonstrated that 34% of patients were lost to follow-up, and that 24% of those followed up had residual disease of the cervix. It was therefore concluded that this form of treatment was inadequate for the hospital population concerned. An additional prospective study was undertaken, as a result of which cryosurgery is recommended only if adequate long-term follow-up is ensured, if skilled colposcopic evaluation is available throughout, and if the disease is limited to mild or moderate dysplasia in younger patients.