The activities of cathepsin B, L, J and H in rat liver were significantly increased by starvation if compared with normal diet rats. Furthermore, the activity of cathepsin L increased with glucagon treatment, and the activities of cathepsin L and H decreased significantly with insulin treatment. The changes in cathepsin B and J activities showed the same tendencies as those of cathepsin L and H, but the differences were not statistically significant. The changes in the activities of cathepsin B and L on starvation corresponded with the changes of enzyme protein amounts judged from Western blotting analysis. The levels of the lysosomal cysteine proteinases and amino acid deaminases in the liver changed in parallel with the hormonal and dietary conditions. The increases of alanine amino transferase activity (AAT) started from a much earlier stage than those of cathepsins under the starvation condition. Although administration of prednisolone caused marked induction of the deamination enzymes such as AAT, the levels of cathepsins in the liver were not changed.