Between 1974 and 1988, 7 myocardial infarctions occurred in 6 (4 men, 2 women) out of 400 systemic lupus erythematosus patients. Their ages at the onset of lupus ranged from 13 to 44 years (m = 26). Four had renal involvement. Control of lupus in all 6 patients required high-dose steroids (at least 1 mg/kg/d of prednisone). Myocardial infarction occurred 4 to 19 years after the onset of lupus (m = 13). One patient died of cardiogenic shock. When the infarction occurred, only one patient was undergoing a lupus flare, while the disease was quiescent or slightly active in the 5 others. One patient had no risk factors for atheroma but had been taking steroids for 10 years. Among the other 4, one had hypertension, another had hyperlipidemia and 3 were smokers; they had been on steroids for 2, 4, 11 and 13 years. Coronary angiogram showed occlusion in all 4, but atheroma in only 2 patients. Lupus anticoagulant was present in 3 of these 4 patients. The mechanisms responsible for coronary occlusion in lupus patients are probably complex and interwoven. In addition to "classical" factors (i.e., vasculitis or steroid-induced atheroma), other factors, such as antiphospholipid antibodies and/or smoking, may play an important thrombogenic role.