The clinical, pathological, and chemical findings in a fatal case of generalized Hand-Schüller-Christian disease in a man of 33 years are presented in case 1. The necropsy examination revealed granulomatous infiltration of the infra-orbital fat, the pituitary stalk, and the posterior lobe of the pituitary and also of the skull bones and the thyroid cartilage. The spinal dura mater contained multiple xanthomatous deposits which had produced degenerative changes in the cord substance by epidural compression. Interesting features were the tumour-like enlargement of the right heart, massive pancreatic and renal infiltration, also heavy constricting xanthomatous mantles which had produced compression of both kidneys and adrenal glands. Case 2 is an example of xanthomatous granuloma, confined to the lungs, in a man of 57 years, and not associated with diabetes insipidus. The histological appearances were those of long-standing chronic xanthoma with marked cystic changes in the lungs, dilated bronchioles, and thick-walled stenosed pulmonary arteries. The pathogenesis of Hand-Schüller-Christian disease is briefly discussed.