OBJECTIVE--To determine the demand placed on local cardiological services by patients prescribed nitrates for ischaemic heart disease. DESIGN--A follow up study of a cohort of patients identified in 1985. SETTING--Nottingham Health District. PATIENTS--Four hundred and ninety nine patients prescribed nitrates in 1985 for presumed ischaemic heart disease. MAIN OUTCOME MEASURES--Referral to medical outpatients, admittance to hospital with chest pain, cardiological investigations, and mortality. RESULTS--Over the seven year period 26% of patients were admitted urgently with chest pain and 15% were referred to the medical outpatient department--a referral rate of 6% a year. 4% of patients had an exercise test and 6% a coronary angiogram. The death rate was 6% a year and a higher proportion died of cardiovascular causes than would be expected in the general population. CONCLUSIONS--Prescription of nitrate is useful in the determination of the prevalence of ischaemic heart disease. Most patients with angina are still treated within the community, and the rate of specialist investigation remains low.