What does the swimming leech have to do with the running human? The ability to move actively in space is essential to members of the animal kingdom, and the evolution of the nervous system relates to a large extent to the evolution of locomotion. The extreme importance of locomotion has stimulated many studies of the neural mechanisms underlying locomotion across a range of species. For the first time, a group of three leading neurobiologists have undertaken a comparative study of these mechanisms. Neuronal Control of Locomotion: From Mollusc to Man describes how the brains in very diverse and evolutionarily removed species control the animal's locomotion. In doing so, the authors reveal unifying principles of brain function, making it essential reading for students and researchers in neurobiology generally, and motor control in particular. In my opinion, the authors have produced a masterful and highly readable exposition on the neural control of locomotion. It is timely and relevant to avant- garde neuroscience. It will have a major impact on the field, and is sure to be referenced well into the second half of the next century. Douglas Stuart, University of Arizona College of Medicine