AbstractA family study of a patient with idiopathic hemochromatosis using noninvasive techniques is presented. All 6 of the patient's asymptomatic children had an increase in transferrin saturation and/or an increase in the absorption of Co57. The Co57absorption test was the most sensitive index of family involvement since one of the children had an increase in absorption at a time when transferring saturation was normal. The family data strongly support the hereditary nature of the disorder, with the mode of inheritance not clearly established from the available data.