Idiopathic infantile arterial calcification is a disorder of unknown etiology manifested by widespread arterial calcification. This usually leads to early death from coronary artery occlusion. In 12 of the 75 cases in the literature, radiographs were taken and it was possible to make the diagnosis in them all. We present two patients, siblings, in whom the diagnosis was established radiologically. The nature of the calcium deposits was studied in one of the infants and proved to be calcium hydroxyapatite. Therapy with diphosphonate was apparently successful in the other child.