Parameters of walking at ordinary, fast and slow speeds in 30 male and 30 female young adults were investigated. More than 10 trials were made for each speed by each subject. The number of subjects and trials was large enough to permit a statistical analysis. The focus of the study was the movement of the point where the resultant foot-ground force intersects the ground. Its pathway, or trajectory, begins at touchdown from the middle part of the heel, then runs quickly on a straight line to the heads of the first or second metatarsal bones, turns medially and moves slowly towards the base of the first toe, ending at the tip of the first or second toe, or between them. This result confirms that the ankle joint works like a hinge during the stance phase, and that the human foot structure is relatively robust. Remarkably high positive correlations between stride length and stature, as well as iliospinal height were found in male subjects. However in females these clear correlations were not found, except at fast walking speeds, although were not so notable as in males. Correlations calculated from the data from all female subjects indicated significantly quite high values, as in males, but it is almost impossible to estimate exact stature or iliospinal height reliably from stride length because of its relative high variation. The sexual difference in walking speed is not due to stride duration, but to stride length.