Many recent reports in the North American literature have documented an increase in the ratio of proximal to distal colorectal cancers with an increase in right-sided lesions. In order to assess trends in the distribution of large bowel carcinoma at our hospital we reviewed the files of 1553 patients who presented with primary colorectal carcinoma over a 30-year period. Thirty-nine percent of patients were over 70 years old and 51% were in the 50-69 year age group. Seventy five percent of the carcinomas were left-sided, 22% right-sided and caecal carcinomas accounted for 18%. This distribution varied only slightly over the study period. Left-sided lesions were more common in males (55%: p less than 0.005), and right-sided lesions were more common in females (57%: p less than 0.005). Caecal carcinoma was more common in patients over 69 years old than in younger patients (p less than 0.001). In elderly females (greater than 69 years) 30% of colorectal carcinomas occurred in the caecum. These findings may have important implications for the investigation of patients with suspected colorectal disease or for screening programmes.