In the literature available hitherto there are many reports on enzymatic changes in tissues and a correlated rise in enzymatic activity in blood serum during experimental and human trichinellosis. In this study we were characterised proteinase activity in crude extracts from muscles of mice infected with Trichinella spiralis and T. pseudospiralis and the dynamics of their changes in different stages of disease. The activity of proteinase in muscle of mice infected with T. spiralis showed an increase in the 1 st- 5th week post infection, and then a slight decrease. The biggest proteinase activity was observed in 5th- 6th week post infection. In the muscle of mice infected with T. pseudospiralis the increase of proteinase activity was observed in 1st-4th week post infection. In the 4th week the activity reached its maximum and in the 5th- 10th week post infection there was a decrease of the activity in comparison with the control. As we could see, the dynamics of the changes of proteinase activity in mice is similar in the case of the disease with other biochemical and immunological indices observed in trichinellosis and with the increase of regeneration and transformation processes observed in histopathological studies