04/21/2004 at 01:00 AM EDT
Dr. Meyer Friedman, the cardiologist who developed the theory that angry, uptight people (whom he said had "Type A" personalities) were more prone to heart attacks than their calmer ("Type B") counterparts, died on Friday in San Francisco. Since the '50s, when his theory was first posted, researchers have debated its merits. Some say that diet and exercise play major roles, too. Then again, Dr. Friedman must have done something right. He was 90.