Seventy-four carcinomas of the anal canal (4,9% of the total number of rectum carcinoma for 1952-1982) were studied, including 45 squamous-cell, 23 adenogenic and 6 undifferentiated carcinomas. Adenogenic carcinomas originated from the rectum mucous membrane over the serrated line; as distinct from carcinomas of other parts of the rectum the mucus-forming and poorly differentiated tumours were predominant among them. Squamous-cell carcinomas originated from the squamous epithelium of the lower part of the anal canal, from the transitional area and from the rectum mucous membrane over the serrated line. They were characterized by peculiarity of their histological structure: they included 11 basaloid carcinomas, 6 carcinomas resembling transitional-cell carcinoma of the urinary bladder, 12 carcinomas resembling carcinoma of the uterine cervix. The problems of the terminology, histogenesis, clinical course of the anal canal carcinoma are discussed.