OBJECTIVE: Women with polycystic ovary syndrome (PCOS) appear to have higher cardiovascular risk than healthy population. Patients diagnosed with PCOS according to the 1990 criteria have a more adverse metabolic profile than those diagnosed with the 2003 criteria. Platelet-derived microparticles (PMPs) appear to contribute to atherosclerosis but have not been assessed in PCOS. The aim of this study was to determine plasma PMPs in PCOS patients. Design A cross-sectional study.METHODS: We assessed plasma PMPs in 76 normal weight women with PCOS (39 belonging to the phenotypes 1 and 2 (group I) and 37 belonging to the phenotypes 3 and 4 (group II)) and 21 healthy normal weight women.RESULTS: Markers of obesity and insulin resistance did not differ between women with PCOS and controls. Serum testosterone levels and the free androgen index (FAI) were higher in group I than in group II and controls (P<0.001 for all comparisons) but did not differ between the latter two groups. Plasma PMPs were higher in group I than in controls (P=0.018) but did not differ between group II and controls or between groups I and II. In the total study population (n=97), plasma PMPs correlated with serum testosterone levels (r=0.207, P=0.042) and the FAI (r=0.207, P=0.042).CONCLUSIONS: Plasma PMPs are elevated in women with phenotypes 1 and 2 of PCOS compared with healthy controls, but not in women with phenotypes 3 and 4. Hyperandrogenemia, which is more pronounced in phenotypes 1 and 2, appears to be implicated in the increase in plasma PMPs.