The beige mouse has been considered as a homologue of Chediak-Higashi syndrome in man. A light microscopic survey of 23 beige mouse tissues, using acid phosphatase as a lysosomal marker, revealed the presence of enlarged (anomalous) lysosomes, often in the form of aggregates, in 15 of the tissues examined. The degree of anomaly varied from one tissue to another and within cells of a given tissue. The most striking alterations occurred in liver parenchymal cells, kidney proximal tubule cells, Purkinje cells and granulocytes. Electron microscopy of liver and kidney revealed enlarged lysosomes containing numerous lipid-like inclusions. The widespread occurrence of anomalous lysosomes strengthens the homology between the beige mouse and Chediak-Higashi syndrome and further supports the concept that lysosomes are intimately involved in this disorder.