Micro-disc electrophoresis was used to study the water soluble proteins of various tissues of the snail Helix Pomatia. The eight areas fractionated were identifiable giant neurons of the metacerebral ganglion, brain, liver, kidney, penis retractor muscle, optic tentacle, oesophagus and heart.The electrophoretic patterns of all tissues showed differences in both slow running and fast running proteins. A large amount of total protein from isolated neurons was associated with the fastest running band which appears to consist of three components. This fast running band was also present in high amounts in brain and optic tentacle and to a lesser extent in heart, penis retractor muscle and oesophagus. Measurements of the band's Rf value, refractionation of isolated bands, and mixing experiments all showed that the fast running band of each of the tissues has the same electrophoretic mobility. This protein band was absent in liver and kidney extracts.On the basis of its distribution, it is suggested that the band is a specific nervous protein.