The appearance of calcific masses within the dermis of scrotal skin is generally referred to as idiopathic scrotal calcinosis. There has been some debate about the pathogenesis of these calcium deposits. This debate centers on the question of whether the calcium deposition is truly idiopathic or whether it occurs as a result of preexisting epidermal cysts. We have performed immunohistochemical staining for keratin in nine patients with apparent idiopathic scrotal calcinosis and have found no evidence of keratin in the dermal tissue immediately adjacent to the calcium deposits. We conclude that idiopathic scrotal calcinosis is idiopathic.