Diagnostic tests that are hazardous or infeasible, or both, may become accepted before inadequacies are recognised; only multicentre trials can provide the necessary information for an unrestricted acceptance of any new diagnostic procedure. We prospectively studied the results obtained in 24 experienced echocardiography laboratories. 2949 tests were done in 2799 patients. In 341 tests (12% of the overall population, 21% of the negative tests) the test could not be completed because of complex ventricular tachyarrhythmias (134, 38% of all submaximal studies); nausea and/or headache (71, 20%); hypotension and/or bradycardia (62, 17%); supraventricular tachyarrhythmias (44, 12%); hypertension (24, 7%); and others (20, 6%). Dangerous events (life-threatening complications or side-effects requiring specific treatment and lasting more than 3 hours, or new hospital admission) occurred in 14 cases (1 every 210 tests)--9 cardiac (3 ventricular tachycardias; 2 ventricular fibrillations; 2 myocardial infarctions; 1 prolonged antidote-resistant myocardial ischaemia; 1 severe, persistent hypotension) and 5 extracardiac (atropine poisoning with hallucinations lasting several hours in the absence of either myocardial ischaemia or hypotension). Life-threatening and/or longlasting complications may occur during dobutamine/atropine stress echocardiography. The test is generally well tolerated, although may be interrupted by minor, self-limiting, usually symptomless side-effects.