Five - Fluorouracil (5 FU) is widely used in oncology, especially in tumors of the gastrointestinal tract and in carcinoma of the breast. Its side effects (gastrointestinal, haematological, alopecia) are well known. However, its cardiac effects are not widely appreciated, despite an incidence similar to that observed with the anthracyclines (1.6% vs 2.2%) and a high mortality rate (12.5%). A new case of coronary insufficiency is reported illustrating the absence of a dose-effect relationship and the frequency of recurrence of symptoms when 5 FU is reintroduced even with coronary vasodilator therapy. The mechanism of cardiotoxicity in this case seems to be coronary spasm.