This study investigates the appropriateness and diagnostic yield of colonoscopy referrals in an African setting using the American Society of Gastrointestinal Endoscopy guidelines: a prospective, descriptive, cross-sectional hospital-based study. A total of 311 patients were included in the study; 228 referrals (73.3%) were considered appropriate and clinically significant pathology was found in 157 patients, giving an overall diagnostic yield of 50.5%. Diagnostic yield in those with appropriate referrals was 58.8% and 27.7% (P = 0.004) in those with inappropriate referrals. In our setting these guidelines are useful in improving diagnostic yield and reducing the rate of inappropriate referrals for colonoscopy. However, patients above the age of 50 presenting with lower gastrointestinal symptoms should undergo a colonoscopy even if the indication was inappropriate, especially in countries which are not implementing colorectal cancer screening programmes for average risk patients.