OBJECTIVE To investigate changes of platelet glycoproteins in patients with diabetes mellitus(DM) type II and their clinical significance. METHODS Seventy DM patients and 28 normal individuals entered in this study. The platelet glycoproteins Ib, IIb, IIIa and P-selectin were analyzed by flow cytometry (FCM). Platelet surface P-selectin was measured by Immunoradiometric analysis (IRMA), and plasma P-selectin concentration by ELISA. RESULTS On FCM, the P-selectin expression on platelets of patients with vascular diseases [(10.28 +/- 4.86)%] was higher than that of normal subjects [(3.75 +/- 1.83)%] (P < 0.01) and patients without vascular diseases [(4.25 +/- 2.29)%] (P < 0.01). Similar results were obtained using IRMA. Plasma P-selectin concentration in patients with vascular diseases [(6.18 +/- 3.20) ng/ml] was higher than that of control group [(3.43 +/- 1.56) ng/ml](P < 0.05) and that of patients without vascular diseases [(3.71 +/- 2.12) ng/ml] (P < 0.05). On the contrary, the platelet surface GP Ib expression in patients with vascular diseases [(86.35 +/- 11.00)%] was remarkably lower than that of normal subjects [(92.63 +/- 7.55)%] (P < 0.05), while platelet GP IIb and IIIa were not changed in any cases. CONCLUSIONS The P-selectin levels in plasma and on platelet surface were increased while platelet membrane GP Ib was decreased in DM type II patients with vascular events.