The influence of pH in the medium on ATPase myosin activity in different muscle types was investigated. It has been found that myosin ATPase had two maxima with different values of the specific activity in cardiac, skeletal and smooth muscles depending on pH, namely: 6.0-6.5 and 9.0-9.5. The dependence of physiological properties of different muscle types on the physical-chemical and structural peculiarities of myosin has being discussed.