Learning to walk is one of the great achievements in human development. An aim of this chapter is to describe the developmental progression of locomotion, ranging from the spontaneous leg kicks of fetuses to the seemingly superhuman abilities of Tarahumaran endurance runners. Our chief aim, however, is to use the development of walking as an exemplar and metaphor for understanding development more broadly. The century-old study of the ontogeny of walking—from the classic descriptions of motor milestones to the modern recognition of the importance of experience in all forms of locomotion—provides one of the clearest, empirically based illustrations of the pragmatic and theoretical issues, methodological advances and conceptual pitfalls, and general principles and processes of development that is available to psychology.