Objective: Factor V Leiden mutation, the genetic defect underlying resistance to activated protein C, is the most common risk factor for venous thrombosis. Factor V Leiden mutation and its relation to post-myocardial infarction (MI) complications including angina pectoris, heart failure, reinfarction and cardiac mortality has not been investigated. We aimed to investigate this relation. Methods: The prevalence of factor V Leiden mutation was investigated in 122 patients with first acute myocardial infarction (aged 56±11, 82 men/40 women). These patients were divided into two groups according to whether the patients had factor V Leiden mutation (Group I) or not (Group II). Post MI complications were evaluated during 18 months. Blood samples from the patients were analyzed for factor V Leiden mutation by DNA analysis, using the polymerase chain reaction (PCR). Results: Factor V Leiden was detected in 11 (9%) patients (aged; 54±10, 5 women/ men) and was not detected in 111(90%) patients (aged; 56±11; 35 women/76 men) of the 122 patients. There were no significant differences between Group I and Group II in terms of post MI complications, including reinfarction (27% vs. 29%; p>0.05, respectively), angina pectoris (45% vs. 38%; p>0.05, respectively), heart failure (27% vs. 23%; p>0.05, respectively) and cardiac mortality (18% vs. 14%; p>0.05, respectively). Conclusion: Post MI complications, including reinfarction, heart failure, angina pectoris and cardiac mortality were not increased in patients with factor V Leiden.