Death directly related to selective coronary arteriography in 5 patients with a history of unstable angina pectoris during the period 1975-1985 is reported. Four different cardiologists were involved. A feature common to all the cases was the presence of significant ostial stenosis of the left mainstem coronary artery (LMCA); 2 patients had haemodynamically important obstruction of a dominant right coronary artery (RCA) ostium, while 2 others had total occlusion in the proximal part of a dominant RCA. The RCA in the last case was angiographically normal and non-dominant. Collateral coronary blood flow was fairly sparse in most cases and in 4 left ventricular dysfunction of varying degree was present. All patients developed severe hypotension and electromechanical dissociation after arteriography while still in the cardiac catheterization laboratory. Resuscitation efforts were uniformly unsuccessful. Autopsy on 1 patient demonstrated extensive obstructive coronary atherosclerosis with a massive acute anterior myocardial infarction. Cardiac catheterization poses an extremely high risk for this subgroup of patients with LMCA disease, as does selective coronary arteriography. The possible role of catheter-provoked coronary vasospasm of the LMCA is suggested; a recently introduced soft-tipped cardiovascular catheter may be more appropriate in this setting.