The temporal relations between the phases of the stride have been investigated in 23 subjects of both sexes and with an age from 20 to 70 years. They were requested to walk freely in five different speeds from very slow to very fast. Equations defining the relations between the different phases of the stride have been set up as well as equations of regression for stride length and cadence versus velocity, for cadence versus stride length and for the phases of the stride versus stride duration. The equations may be used to predict expected values from known velocities and stride durations in pathological cases and help to explain the interaction between different phases of the stride. In pathological cases they may therefore be used for a better understanding of the dynamic relations between the primary disturbance and the compensating postural reactions.