The presence of a great variety of neuron-specific phosphoproteins in nervous tissue supports the view that protein phosphorylation plays many roles in neuronal function. The physiological significance of several of these phosphoproteins has already been established. Some neuronal phosphoproteins have been detected throughout the entire nervous system, whereas the distribution of others is limited to one or a few neuronal cell types. These various neuron-specific phosphoproteins are proving of value in the study of the physiology, anatomy, developmental biology, and pathophysiology of the nervous system.