Objective: We aim to demonstrate diagnostic accuracy of serial MPV measuring and to assess its correlation with cardiac troponin I (cTnI) levels. Design: Cross-sectional study. Methods: Consecutive patients presenting to emergency department with new onset chest pain started in the last four hours without electrocardiographic ST segment and T wave changes, pathological q waves were included in study. Complete blood count and cTnI levels were studied on admission and six hours after presentation. Patients with cTnI levels higher than 0.06 ng/ml were diagnosed as non-ST elevation myocardial infarction (NSTEMI) and other patients were matched as the control group. Results: NSTEMI group had significantly higher levels of MPV on admission and at the sixth hour. The increase in MPV was corraleted with elevation of cTnI levels. At six hours follow up, the increase in MPV levels predicted myocardial ischaemia (corrected r(2)=0.36; p=0.001) in linear regression analysis. The corresponding area under the receiver operating characteristic curve (ROC) for admission MPV, sixth hour MPV and increase in MPV levels in predicting myocardial ischaemia in patients with increased cTnI were 0.652, 0.727 and 0.896 respectively. If MPV threshold was selected as >= 0.10 fL during follow up, myocardial ischaemia was predicted with a sensitivity of 75% and specificity of 88%. Conclusions: Elevation of MPV levels in patients with acute chest pain may be an indicator of myocardial ischaemia. Serial MPV measurement can be used to complement serial cTnI measurements to diagnose NSTEMI.