Metal powders may be produced electrolytically by two different methods: (a) direct deposition on the cathode, and (b) grinding of a brittle deposit. The principles underlying method (a) are dealt with in this paper. Three factors are shown to be responsible for the formation of powdery or spongy deposits: (1) low metal overvoltage, (2) depletion of the metal content of the cathode film, and (3) hydroxide formation in the cathode film. These factors may operate together or they may be operative under different conditions of electrolysis. Powder formation on the cathode in the electrolysis of copper, iron, nickel, zinc, and cadmium is described and analyzed.