Upon activation platelets shed membrane components containing certain membrane receptors and other proteins inherited from parental cells. These components are called platelets-derived microvesicles (PMVs). We present flow cytometric assay for immunophenotyping of PMVs in platelet rich plasma concentration of patients without signs of inflammation and with significant abnormalities of blood clottinig and in increased C-reactive protein (CRP) concentration. The assay has been used to study PMVs counts in non-stimulated samples of isolated platelets and short time after thrombin stimulation. In both studied groups the number of PMVs was decreased after thrombin stimulation. This phenomenon was probably dependent on procoagulative thrombin properties and was clearly seen in control group. In both studied group thrombin-stimulated platelets delivered more PMVs expressing activation marker CD62P but only in control group under influence of stimulation the number of CD41+ CD62P+ An+ PMVs increased. Obtained results suggest that increased CRP concentration accompanying inflammation decreased free PMVs deliveration as well as changed platelets reaction to thrombin stimulation.