Gelatinolytic and collagenolytic proteinases were separately isolated by different extraction methods from the mouse ascites hepatoma MH134, and from rat ascites hepatoma AH109A. The activities of two proteinases in each extract showed no significant differences, but after trypsin activation the activities of proteinases from the highly metastatic MH134 were significantly increased compared to the enzyme activities in AH109A, which has low metastatic potential. The total activities of collagenase and gelatinase were increased 7.2- and 5.1-fold; their specific activities were increased 5.2- and 4.8-fold, respectively. Gelatinase and collagenase from MH134 were characterized on gelatin zymography. The gelatinase had a molecular weight of 99 and activation by 4-aminophenylmercuric acetate (APMA) or trypsin resulted in its conversion to 79 or 79-95 kD, respectively. The collagenase revealed a major gelatinolytic band at 89 kD, which was converted to 85 and 70 kD by APMA-activation, and a minor gelatinolytic band at 60 kD. These proteinases could degrade native type I collagen to small fragments in a cooperative manner. Trypsin inhibitor, which affects the trypsin activation of latent gelatinase, was extracted together with gelatinase. The inhibitory activity of the enzyme from AH109A showed a 4.1-fold higher specific activity and 3.7-fold greater total activity than that from MH134. The proteinase(s) capable of activating the gelatinase was also extracted from MH134.