To evaluate the contribution of hematologic factors and longterm inflammation to the development of myocardial infarction at a young age, we measured hematolo gic variables, including soluble fibrin and high-sensitivity C-reactive protei n, in 90 patients who had myocardial infarction and 138 controls ≤45 years of a ge. Plasma levels of soluble fibrin and C-reactive protein were significantly h igher in patients than in controls. On multivariate regression analysis, soluble fibrin was the strongest predictor of myocardial infarction at a young age. To evaluate the contribution of hematologic factors and longterm inflammation to the development of myocardial infarction at a young age, we measured hematolo gic variables, including soluble fibrin and high-sensitivity C-reactive protei n, in 90 patients who had myocardial infarction and 138 controls ≤45 years of a ge. Plasma levels of soluble fibrin and C-reactive protein were significantly h igher in patients than in controls. On multivariate regression analysis, soluble fibrin was the strongest predictor of myocardial infarction at a young age.