Polyvalent intravenous immunoglobulin (IVIg) is considered to be standard therapy for a variety of autoimmune and idiopathic disorders. Several reports have emphasized the temporal association between administration of IVIg and thrombotic events. Recent experience with a patient who suffered a large myocardial infarction shortly after receiving IVIg led the authors to review the clinical and basic literature on administration of IVIg as a possible precipitant for myocardial infarction. Although the existence of an association between IVIg administration and myocardial ischemia has not been demonstrated in clinical trials, a body of clinical experience has begun to accumulate that is suggestive of an association between IVIg administration and cardiac and cerebral ischemia in older individuals or individuals with a known history of ischemic disease. Basic research demonstrating that IVIg administration may increase blood viscosity suggests that such an association is plausible.