Platelet retention by glass-bead columns was measured in 174 patients undergoing coronary arteriography. Coronary lesions were found in 116 patients; 58 did not have visible lesions. Patients were further subdivided on the basis of age, sex, glucose tolerance, and serum lipoprotein pattern. No differences in mean platelet adhesiveness were found on the basis of age or coronary artery disease. A trend toward higher platelet adhesiveness was seen in patients with either type IV hyporlipoproteinemia or with abnormal glucose tolerance. Platelet adhesiveness was higher in all male subgroups except for a female subgroup with abnormal glucose tolerance. Mean platelet adhesiveness in this group was significantly higher than in female patients with normal glucose tolerance and equaled levels found in male patients with abnormal glucose tolerance. The results of this study are consistent with earlier investigations which found a disproportionate risk for the development of atherothrombotic events among female patients with diabetes mel itus.