History and admission findings: A 32-year-old smoker was referred to our hospital for the evaluation of acute chest pain. 9 years earlier he had had a non Q-wave myocardial infarction. At that time, angiography showed widely patent coronary arteries without atherosclerotic lesions. Investigations: Electrocardiographic as well as creatine kinase patterns were consistent with an acute transmural myocardial infarction. Cholesterol, triglyceride und homocystein levels were normal. The patient was homozygous for the factor V Leiden mutation. Treatment and course: Thrombolysis was performed with streptokinase followed by coronary angiography showing a patent left coronary system and a non-occlusive thrombosis in the distal part of the right coronary artery. Body weight adapted abciximab infusion was started immediately. 9 weeks later coronary angiography was repeated. Now, in the distal part of the right coronary artery a minor dissection was seen followed by a not flow-limiting stenosis. Conclusion: On the evidence of this case history, we think it possible that the pronounced thrombophilia created by the homozygous factor V Leiden mutation may provoke myocardial infarction even if the atherosclerotic lesions are still too trivial to be detected by angiography.