Patients with diabetes mellitus develop hypercoagulability, platelet hyperaggregability and premature atherosclerosis [1±4]. Atherosclerosis is the major cause of death in patients with diabetes mellitus, leading to a high mortality rate in all forms of the disease [5]. Classical risk factors, including hyperlipidaemia, hypertension, and obesity, do not completely account for the increased incidence of atherosclerosis associated with diabetes [6]. Recent reports suggest that increased expression of endothelial adhesion Diabetologia (2002) Results. The concentration of MDMPs in diabetic patients was higher than in normal subjects. We found no differences in the binding of anti-GPIIb/IIIa and anti-GPIb monoclonal antibodies between groups. There were differences, however, in the concentrations of PDMPs, plt-CD62P, and plt-CD63 between Type II (non-insulin-dependent) diabetes mellitus patients and control subjects (PDMPs: 585 25 vs 263 9, p < 0.01; plt-CD62P: 28.1 % 1.4 % vs 9.4 % 0.6 %, p < 0.001; plt-CD63: 28.1 % 1.4 % vs 8.6 % 0.5 %, p < 0.001). Amounts of MDMPs correlated positively with these platelet activation markers, and the relation between PDMP and MDMP was the most significant. The concentration of MDMP in patients who had diabetes complicated with nephropathy, retinopathy, or neuropathy was higher than in those without diabetes-related complications. The increase in MDMP was particularly significant in patients with nephropathy. Concentrations of sE-selectin were higher in Type II diabetes patients than in control subjects, and correlated with MDMP, PDMP, plt-CD62P, and plt-CD63 levels in nephropathy patients. Conclusion/interpretation. In Type II diabetes patients, we detected increased activation of monocytes, which could have been stimulated by activated platelets and PDMPs. Because the activation of monocytes is associated with vascular endothelial damage, high concentrations of MDMPs could indicate vascular complications in diabetes patients, especially those who have diabetes-related nephropathy. [Diabetologia (2002) 45:550±555]