OBJECTIVE--To compare the usefulness of high dose dipyridamole stress echocardiography with dipyridamole stress electrocardiography and exercise electrocardiography for the evaluation of coronary artery disease. DESIGN--Prospective investigation with coronary angiography as the criterion standard and blinded assessment of study data. SETTING--Cardiology unit of a tertiary referral centre. SUBJECTS--Fifty eight patients with suspected coronary disease; three of these were excluded because of poor echogenicity at baseline (test feasibility 95%). Angiography showed normal coronary arteries in 15 and coronary disease (greater than or equal to 70% diameter stenosis) in 40. INTERVENTIONS--Cross sectional echocardiography and 12 lead electrocardiography during dipyridamole stress (up to 1 mg/kg) and exercise electrocardiography on a separate occasion. Wall motion was analysed with an 11-segment model developed at Hammersmith Hospital. MAIN OUTCOME MEASURES--Test sensitivity, specificity, and side effect data. RESULTS--16 of 40 patients with coronary artery disease had inducible asynergy; all had multivessel disease and a tight stenosis in the vessel that supplied the abnormal segment. Exercise duration and time to 1 mm ST segment depression were significantly shorter in patients with a positive echocardiogram than in those without (both p less than 0.01). The sensitivity and specificity of dipyridamole stress echocardiography were 40% and 93% respectively; sensitivity improved to 60% when baseline (n = 18) or reversible asynergy defined an abnormal study (likelihood ratio = 9). Corresponding figures for stress electrocardiography were 38% and 80% for dipyridamole and 80% and 67% for exercise. Adverse reactions were seen in 67% of patients and included two instances of pronounced hypotension, one episode of prolonged myocardial ischaemia, and one cardiac arrest in a patient who was successfully resuscitated. CONCLUSION--A positive high dose dipyridamole echocardiogram predicts multivessel disease and impaired coronary reserve, but low overall sensitivity and occasionally troublesome side effects limit its clinical usefulness.