Twenty-five patients with squamous-cell or cloacogenic carcinomas of the rectum were evaluated by computed tomography (CT). Seven patients were studied before and 19 after treatment. CT provided excellent definition of tumor extent, including local spread, lymph node involvement, and distant metastases. In one of seven pretherapy studies, CT findings significantly altered patient management. Tumor recurrence was correctly identified in 14 of 19 patients having posttherapy scans, although CT-guided biopsy was required to confirm the presence of malignancy in three cases. Four scans were false positive. Extensive soft-tissue stranding in the ischiorectal fossa and/or perirectal fat associated with a large focal mass occurred in all patients with local tumor recurrence. Stranding was also seen in all patients treated with radiation. CT is an excellent method for preliminary evaluation and follow-up of patients with anal epithelial neoplasms, facilitating rapid and effective management.