Because of its neurocrest APUD origin, malignant melanoma has been postulated to be a component of the multiple endocrine neoplasia (MEN) syndromes; however, such a case has not been previously described. Prior associations of melanocytes with the MEN syndromes have been confined to hyperplasia. This report describes the first case of malignant melanoma occurring in a patient with the MEN IIA syndrome (bilateral pheochromocytomas and medullary thyroid carcinoma). The role of melanocytic hyperplasia and neoplasia within the MEN syndromes is discussed.