Treatment failure for intraepithelial neoplasia of the uterine cervix following electrocautery, cryosurgery, or carbon dioxide laser therapy is related primarily to incomplete eradication of the lesion. This may be due to the depth of crypt involvement, the linear extent, or the location of the abnormal epithelium. In view of this, the extent (depth and linear extent) and the location of cervical intraepithelial neoplasia (CIN) in 319 cervical cone specimens were analyzed. There is a significant correlation between the severity and the extent of the change. The mean depths of CIN I, II, and III were 0.42 +/- 0.28, 0.93 +/- 0.71, and 1.35 +/- 1.15 mm, respectively. The mean linear extents for CIN I, II, and III were 4.10 +/- 2.84, 5.84 +/- 4.13, and 7.60 +/- 4.32 mm, respectively. To eradicate 99.7% of CIN III lesions, it is necessary to destroy the tissue up to 4.80 mm in depth and of sufficient linear extent. While most lesions (87.2%) involved the transformation zone, 9.7% were higher in the cervical canal and 3.1% were located in the ectocervix. Appropriate cytologic samples, endocervical curettage, and colposcopic examination should be employed in evaluating the CIN, and strict criteria should be followed in selecting the patients for conservative management.