The 1991 Bethesda System states that atypical squamous or glandular cells of undetermined significance should be further classified as reactive or premalignant/malignant. The validity of this qualification for identification of patients with cervical intraepithelial neoplasia (CIN) was tested. One hundred twenty-four cytologic smears with squamous atypia were reviewed retrospectively by two cytopathologists blind to the colposcopy results. The smears were classified as favoring either reactive or premalignant/malignant processes. Subjective criteria used in the classification were based on the pathologists' experience. All patients underwent colposcopy and selected biopsy under the direction of a gynecologic oncologist. Of the 124 atypical smears, 69 were classified as favoring reactive processes and 55 as favoring premalignant/malignant processes by cytopathologist 1. Cytopathologist 2 classified 68 as reactive and 56 as premalignant/malignant. Colposcopy and selected biopsy revealed the following lesions: 34 cases of human papillomavirus (27.4%), 17 of CIN 1 (13.7%), 4 of CIN 2 (3.2%), 2 of CIN 3 (1.6%) and 67 without pathology (54.0%). All six patients with squamous atypia and underlying CIN 2 and 3 lesions had their cytology classified as premalignant/malignant by the cytopathologists. In these patients this qualification had high sensitivity (100%) and negative predictive value (100%). The 1991 Bethesda System classification above, when applied to patients with squamous atypia, was effective in identifying patients with serious pathologic cervical lesions. If used as a triage method, colposcopy should be reserved for atypical lesions classified as premalignant/malignant, potentially decreasing the cost of health care without decreasing the quality of that care.