A retrospective analysis of 640 patients who underwent 681 colonoscopic examinations between March 1984 and April 1996 was undertaken. The major indications were rectal bleeding (32.8%), change in bowel habit (24.7%), abdominal pain (20.1%), abnormal barium enema (9.8%) and iron deficiency anaemia (4.8%). Total colonoscopy was performed in 79.3% of cases. The colonoscopic finding was normal in 49.8% of patients. Most of the lesions were benign. Polyps and carcinoma were found in 9.2% and 7% of patients respectively. 91.3% of the lesions were located distal to the splenic flexure and of the remaining proximal lesions, polyps and carcinoma accounted for only 2.2%. Rectal bleeding produced the highest diagnostic yield (70%) followed by iron deficiency anaemia (61.3%), change in bowel habit (48.1%) and abnormal barium enema (47.6%). Lower yields were found in patients with abdominal mass (33.3%), follow up colonoscopy (28.6%) and abdominal pain (26.9%). However, the diagnostic yield of clinically significant pathology varied widely among the different indications. Therefore, selection of patients for colonoscopy based on the diagnostic yield of each indication may not be practical. Sigmoidoscopy is suggested as the first line of investigation for patients suspected to have colonic diseases, particularly where there is limited trained manpower and facility. Total colonoscopy should be reserved for sigmoidoscopy negative patients with persistent symptoms and high risk cases for malignancy.