The platelet indices Mean Platelet Volume (MPV), Platelet Distribution Width (PDW) and Plateletcrit (PCT) provided by automated hematology analysis are rarely used in clinical practice. Platelets play a central role in the pathogenesis of acute coronary syndromes (ACS) and high MPV has been associated to more reactive platelets and regarded as an independent risk factor for myocardial infarction. In this study, platelet indices were evaluated in 39 patients with ACS presenting two altered biochemical parameters, C reactive protein (CRP) and creatine kinase fraction MB (CK-MB). The results obtained showed significantly higher MPV and PDW values in the group with ACS in comparison to the control group. Also observed was a weak but significant positive correlation between MPV and CK-MB. In view of findings of previous studies, which have associated macroplatelets with higher thrombotic potential our results suggest that the use of the MPV and PDW indices as additional and complementary markers may contribute to the investigation and followup of thrombotic risk in patients with ACS.