Since few autopsy data are available on the cause of death in joggers, 30 joggers who underwent autopsy were studied. All were males 18 to 57 years of age (mean 36 years). Information on jogging habits was available in 18 patients who ran 7 to 105 miles per week (mean 33) for one to 28 years (mean 20). Three of the 30 patients were "marathon runners." In 12 patients, the only available information was that they had been jogging for at least six months, but information regarding the distance run was not available. Sixteen patients (53 percent) had clinical histories of systemic hypertension, hypercholesterolemia and/or family histories of coronary heart disease; eight patients had a previous history of coronary heart disease; two had transient ischemic attacks. Nineteen patients died suddenly while jogging; six died suddenly after jogging; three noted chest pains soon after jogging; two were found dead in bed. The heart weights were increased in 16 (53 percent). Twenty-two patients (73 percent) had severe coronary artery atherosclerosis, six of whom had coronary artery thrombi; acute and/or healed myocardial infarction was present in 14 (47 percent). One patient had a floppy mitral valve. In seven patients, no cause of death could be established; three of these had cardia hypertrophy and six had myocytolysis. Myocytolysis was also noted in 11 patients with severe coronary atherosclerosis. Severe coronary artery atherosclerosis was the major finding (73 percent) in the 30 joggers in this series.