A community based survey of coronary heart disease (CHD) was carried out on a random urban sample of 13,723 adults in the age group 25-64 yr in Delhi, India. CHD was diagnosed either on the basis of clinical history supported by documentary evidence of treatment in a hospital or at home; or on ECG evidence in accordance with the Minnesota Code. The overall prevalence of CHD based on clinical history, was 31.9 (39.5 in males and 25.3 in females) per 1000 adults in this age group. The number of patients with CHD increased with advancing age in both sexes. The total prevalence rate based on both clinical history and ECG criteria (asymptomatic patients with ECG changes of definite myocardial infarction and ST-T changes suggestive of CHD) was estimated as 96.7/1000 adults in this age group. Analysis of information on socio-economic status, family history of CHD, obesity, hypertension and smoking obtained from this sample of 13,723 adults suggested that hypertension had the strongest association with CHD. Obesity, diabetes and family history were also found to be associated with CHD. It should, however, be noted that risk factor assessments in CHD can be done satisfactorily only through incidence studies.