THIS PAPER deals with the description of clinical, pathologic, histochemical and biochemical findings in two cases of generalized xanthomatosis with calcification of the adrenals. The infants were siblings of a previously described patient,1 and and the findings warrant the conclusion that the disease process was identical in all three. The study of these cases and review of pertinent literature indicates that primary xanthomatosis (idiopathic lipidosis with deposition of cholesterol and triglycerides) is a metabolic disease entity that is independent of the granulomatous process called histiocytosis X, or eosinophilic xanthomatous granuloma. It will be shown in the discussion that primary xanthomatosis may occur in various forms, and that the form described in this paper is a rare but distinct clinical and pathologic type. This type differs in the distribution of lesions from other types of primary xanthomatosis, such as the type of cerebral xanthomatosis described by van Bogaert, Scherer and Epstein, and the type associated with involvement of bones that sometimes produces the Hand-Schüller-Christian syndrome. For reasons that wiil be clarified in the discussion, the term "Hand-Schüller. Christian disease" is not adopted in this paper. The term "Hand-Schüller-Christian syndrome" indicates a well-known syndrome with exophthalmos, diabetes insipidus and peculiar bone changes. The term "primary xanthomatosis" describes a primary (i.e., idiopathic) storage process in which triglycerides and cholesterol are deposited in various tissues. CASE REPORTS Case 1 Family History: The two infants described in this article and the infant previously described1 were female siblings born to closely related parents. The father and mother, both Persian Jews, were cousins.