CT is well known modality for detecting of rectal anal cancer. Nineteen cases of anal and reactal cancer wereanalyzed about perirectal invasion, metastasis, and defined their staging by CT. The results were as follows: 1.The CT scans demonstrated primary cancer of anus and rectum in all cases, and correctly staged in 14 patients (74%). 2. The CT showed an accuracy for detecting lymphnode involvement of 68%, and perirectal invasion of89%. 3. The perirectal invasion suggests a metastasis ot lymphnode or other organs.