['To determine the proportion of platelets and fibrin in coronary thrombi.', 'Immunohistochemical and morphometric means to examine the coronary arteries of 31 patients who died of acute myocardial infarction.', 'Fresh thrombi were detected in the feeding arteries of infarction areas in 23 cases (74%) and were associated with plaque rupture in 18 (78%) and plaque erosion in 5 (22%). An immunohistochemical study showed that the thrombi consisted of a mixture of fibrin and platelets as well as some other types of blood cells. The fibrin and platelet positive areas in the thrombi associated with plaque rupture accounted for 74 (19)% and 35 (20)% (p < 0.01) and those associated with erosion accounted for 51 (6)% and 70 (21)%, respectively, of the total areas. Areas of positive immunoreactivity for tissue factor and C reactive protein were also significantly greater in ruptured than in eroded plaques.'] Does proportion of fibrin and platelets differ in thrombi on ruptured and eroded coronary atherosclerotic plaques in humans?