An illustration is given of how the three major forms of vertebrate locomotion may be understood. It is suggested that swimming by lateral undulations, jumping and quadrupedal progression can be produced through the very same spinal cord design and vestibular organization. All three forms of locomotion are described in terms of waves of neuronal activity dependent on the stretch and tension of trunk musculature. Musculature of the right and left half of the body are antagonistic in swimming by lateral undulations; musculature of the dorsal and ventral trunk are antagonistic in jumping locomotion; and musculature of the right dorsal and left ventral compartments are antagonistic to the left dorsal and right ventral compartments during the twisting action of quadrupedal progression. It is emphasized that no changes in spinal or vestibular action are needed to accommodate any form of locomotion. Only differences in proprioceptive input are required. An initial statement is given of the relation between basic vestibular reflexes and the forms of locomotion. It is obvious that the locomotor rhythms are consistent with basic spinal as well as vestibular reflexes.