Separate components of acid-base balance in blood (ABR)-pH, pCO2, BE, SB, BB-were studied during the long-term drill of service dogs of two age categories. These service dogs were included in two different work strain groups (patrol dogs and searching dogs). The results of long-term drill demonstrated, in particular, significant changes in dynamics of pH and pCO2. The pH values were permanently raised as compared with reduced pCO2 values during the whole period of 130-days exercise and as compared with the initial values. Other components of acid-base balance in blood do not show such variations (patrol and searching dogs) and these components justify that the adaptation of organism to the given strain gained suitable stabilisation. For studying the psychical and physical strain in service dogs it is recommended to include pH and pCO2 in the tests.