Spontaneous coronary artery dissection is described in eight patients 26 to 47 years of age. Six died suddenly, and two died after the onset of chest pain. All had normal heart weights and all had dissection of left anterior descending coronary artery, which occurred mainly in the outer one third of the media. The adventitial of the dissected artery contained inflammatory infiltrates which were predominantly eosinophilic granulocytes. Forty-six cases previously published in 32 reports are reviewed. It is suggested that adventitial eosinophilic infiltrate may be responsible for spontaneous coronary artery dissection.