Gastrointestinal hemorrhage is an exceptional complication of antiphospholipid syndrome and most reported cases are secondary to ischemic lesions. Brunner's gland hyperplasia is an infrequent and usually asymptomatic condition that has been associated with chronic renal failure. We report a patient with primary antiphospholipid syndrome who, after mechanic heart valve replacement and while in a state of drug-induced anticoagulation, experienced a life-threatening upper gastrointestinal hemorrhage due to nodular hyperplasia of Brunner's glands. This entity may be considered in the differential diagnosis of upper gastrointestinal bleeding in patients with antiphospholipid syndrome, most of whom are treated with oral anticoagulatory drugs, and particularly in patients with chronic renal failure.