An enzyme histochemical study was carried out on fat-storing cells, which are distributed in the space of Disse of mammalian liver. The livers used for study consisted of human autopsy materials demonstrating either acute or chronic circulatory disturbance. Fat-storing cells contain abundant glycogen, and demonstrate a marked gamma-glutamyl transpeptidase activity and a weak lactate dehydrogenase activity. It is highly probable that an active glyconeogenesis rather than glycogenolysis is being carried out in these cells. In acute circulatory disturbance, an elevated alkaline phosphatase activity is found in the wall of sinusoids. This phenomenon is a manifestation of activated capillary endothelial cells participating in the regeneration of liver parenchyma. On the other hand, in chronic congestive liver, elevated gamma-glutamyl transpeptidase activity in fat-storing cells is concerned in the proliferation of fibers in the wall of sinusoids, and elevated pressure in sinusoids is considered to be the main factor in its increased activation.