In a cross-sectional survey, we estimated the prevalence of coronary heart disease in a sample of 975 middle-aged males (35-59 years), from a defined population in the Central province of Sri Lanka using the London School of Hygiene cardiovascular questionnaire and a 12-lead electrocardiogram. The estimated prevalence rates were: (a) Definitive evidence of ischemic heart disease (positive symptoms and ECG changes of ischemia), 16/1000 (95% C.L., 9-27). (b) Evidence of coronary heart disease based on history alone 54/1000 (95% C.L., 40-71). (c) Estimate based on ECG changes of ischemia without symptoms 32/1000 (95% C.L., 21-46). Median values for major risk factors were: systolic blood pressure 120 mmHg, diastolic blood pressure 88 mmHg, serum cholesterol 4.99 mmol/l, high density lipoproteins 0.99 mmol/l and body-mass index 20.4 kg/m2. About half (57.9%) the subjects were current smokers, 17% had actual hypertension (systolic blood pressure > 159 mmHg and/or diastolic blood pressure > 94 mmHg and/or been treated for hypertension), 12.6% had hypercholesterolemia (serum cholesterol levels > 6.5 mmol/l), 18.4% had a body-mass index > 24 kg/m2 and 5.8% were diabetic. Hypercholesterolemia (> 6.5 mmol/l), a higher body-mass index (> 24 kg/m2) and diabetes were more prevalent among subjects living in an urban rather than a rural environment.