During follow-up examinations; 1,338 cervicovaginal cytologic smears were obtained from 254 women who had irradiation therapy for cervical cancer. These specimens were meticulously searched for the various cellular phenomena that may characterize such preparations, and some of the findings were subjectively quantitated. Correlations were made with histopathologic diagnoses, clinical findings, and results of treatment. Patients with malignant postradiation cells who were promptly treated for latent new or recurrent tumors generally responded well to treatment of the secondary tumor. The presence of malignant cells at any time after completion of therapy is an ominous sign, irrespective of the clinical status, and should lead to intensive effort to identify the site of a new or persisting lesion. The significance of dysplasia in postradiation smears is not entirely clear, and in certain instances it is difficult to distinguish severely dysplastic cells from either repair cells or malignant cells.