A young man without heart disease with a metastatic carcinoma of the pancreas received a 5-Fluorouracil therapy (25 mg per kilogram body weight/24 h by continuous infusion over a period of 5 days). Approximately 56 h after beginning of the first cycle of therapy (after 36 h of the second cycle) he complained of severe chest pain, which did not respond to nitrates, improved after application of opioids, and subsided definitely after termination of the 5-FU infusion. During the periods of pain, the ECG and the creatine kinase were normal. At a later time, finally, a scar in the posterior wall of the myocardium was detectable in the ECG. When repeating the 5-FU infusion, similar problems arose with less intensity. The patient died as a consequence of the progress of the tumor disease. At autopsy, two myocardial infarctions were detectable. There was no demonstrable stenosis of the coronary arteries. Spasms of the coronary arteries are discussed as a cause of this side effect of 5-FU-therapy.