Diabetes mellitus was provoked by intraperitoneal introduction of 40 mg of streptozotocina to 80 white rats at the age of 6–8 months. The activity of proteases in the gomogenates of a liver was studied in 10 and 25 days after the drug introduction, and in blood serum with the help of kasein splitting (pH 7.6). It was established that development of experimental diabetes decreased the proteolytic activity in pancreas and increased in a liver after 10 days, after 25 days all returned to norma and sharply (aprox. in 3 times) decreased the activity of proteases in liver. Biologically active supplements didn’t influence proteolytic activity.