In vitro preparations of the nervous system, which were originally developed for investigations of invertebrate neural networks, have recently gained popularity for studying locomotor networks in the vertebrate nervous system. The nervous system is removed from the animal and maintained in a physiological bathing solution. These preparations can be induced to generate locomotor patterns in a number of ways and offer several unique advantages. The function of the motor networks can be manipulated by alterating the composition of the bath, and immobilization of the preparations, either by cutting ventral roots or bath application of curare, greatly facilitates intracellular recordings. In vitro preparations offer the opportunity to acquire the detailed information necessary for understanding vertebrate motor networks at the cellular level. This article reviews some of the many applications of in vitro preparations for studying vertebrate locomotor control using examples derived mainly from work on the lamprey.