Six hundred five women with varying degrees of intraepithelial neoplasia of the uterine cervix were treated with 4 different modalities: 315 patients were treated with cryosurgery, 43 with electrocautery, 127 with conization, and 120 with hysterectomy. Of the patients undergoing cryosurgical treatment, 83 had cervical intraepithelial neoplasia (CIN) I (mild dysplasia), 172 had CIN II (moderate dysplasia), and 60 had CIN III (severe dysplasia and carcinoma in situ). Patients undergoing electrocautery all had either CIN I or II. Of 247 patients undergoing conization and hysterectomy, all had CIN III except for 2 with CIN II. A follow-up study revealed a failure rate of 5.5% in CIN I or II and of 15.5% in CIN III among patients with cryosurgical treatment. Following conization for CIN III, 12.5% of patients had treatment failure; no treatment failure was reported among patients who underwent hysterectomy for CIN III. Cryosurgery and conization were equally successful in treating CIN III. Cryosurgical therapy of CIN is therefore an effective means of treatment, but a precise diagnosis must be established by colposcopy and colposcopically directed biopsy before therapy. Also, restricted criteria should be used with regard to the geographic extent of the disease, and endocervical curettage should be performed as part of the evaluation of patients with CIN undergoing cryotherapy.