An increase in mean platelet volume has been reported to be associated with arterial thrombosis and myocardial infarction. A larger mean platelet volume has been regarded as an independent risk factor for recurrent myocardial infarction. We therefore investigated whether it is also increased in patients with coronary heart disease examined a few days before cardiac surgery. Four hundred and twenty-six patients with coronary heart disease who were waiting for cardiac surgery and 125 healthy individuals were included in the study. Mean platelet volume and other platelet parameters were obtained from a routine blood count procedure using a flow cytometric haematology analyser. Mean platelet volume did not differ significantly between patients and controls; however, as expected from the literature, patients had significantly elevated levels of fibrinogen, cholesterol, triglyceride, apolipoprotein B and apolipoprotein(a). Furthermore, we observed no significant difference in mean platelet volume between patients without myocardial infarction and those who had survived at least one myocardial infarction. Our findings suggest that, using a routine laboratory procedure, mean platelet volume cannot be used as a predictive marker for coronary heart disease or myocardial infarction.