In three young fox terriers a lipid storage disease is reported. This thesaurosis is almost identical to Wolman's disease in children. Clinically and pathologically hepatosplenomegaly is the most striking feature. Morphologically the disease is characterized by extensive lipid deposition mainly in liver, spleen, lymphnodes, intestinal mucosa, and bone marrow. Circular corneal lipid deposit (Arcus lipoides corneae) is of diagnostic significance. Some of the material has the typical structure of cholesterol crystals. Under polarized light the deposits consist of birefringent and non-birefringent lipids. All three dogs with lipid storage disease have one common ancestor. In addition their pedigrees reveal close relationship amongst the nearer forefathers and the affected animals themselves. From analogy with human Wolman's disease it is concluded, that in the Foxterrier, too, this lipid storage disease is caused by an inheritable deficiency of acid esterase. The mode of inheritance of this inborn lysosomal disease is probably autosomal recessive.