Four gingivain proteases, active in presence of L-cysteine, were purified from spent culture media of oral pathogen Porphyromonas gingivalis by ion-exchange chromatography on MonoQ and chromatofocusing on MonoP columns. Three of the purified proteases, with molecular masses of 75 kDa, 70 kDa and 55 kDa, respectively, hydrolyzed synthetic chromogenic substrates with arginine in the P1 position. One protease, with a molecular mass of 80 kDa, hydrolyzed substrates with lysine in the P1 position. It is proposed these enzymes be named: arg-gingivain-75, arg-gingivain-70, arg-gingivain-55, and lys-gingivain-80, respectively, based on their molecular mass and specificity for either arginine or lysine in the P1 position.