Fundic mucosal extracts of the cat were examined by chromatography using DEAE-cellulose at pH 5.3. The peaks of proteolytic activity located by this method were shown to be heterogeneous on electrophoresis. By electrophoresis of individual homogenous chromatographic fractions 9 separate zones of proteolytic activity were detected. One zone did not migrate from the origin and is possibly a non-pepsinogen gastric protease. Simultaneous electrophoresis of pepsinogens and pepsins indicated that each pepsinogen gave rise to one pepsin. One zymogen gives rise to a pepsin active with the synthetic substrate acetyl-L-phenylalanyl-L-diiodotyrosine (APDT).