The activities of tyrosinase, invertase, trypsin and chymotrypsin were studied after exposure to one or more of the following high-pressure inert gases: N20 at 600 psig or NI or Ar each at 5000 psig. Exposure to high-pressure nitrogen or argon failed to significantly inhibit the rate of tyrosinase activity in fluid systems. However, the rates of tyrosinase-catalyzed reactions in shell-cast gelatin gels were significantly depressed by exposure to high-pressure nitrogen, and even more so by high-pressure nitrous oxide. This inhibition proved to be oxygen dependent and reversible. Pressurization experiments with invertase, trypsin and chymotrypsin indicated that high-pressure N20 did not significantly inhibit these enzymes. This fends support to the hypothesis that highpressure inert gases inhibited tyrosinase activity in nonfluid systems by decreasing the availability of oxygen, rather than by physically altering the enzyme. It must be concluded that there is little hope that the enzymes in food systems can be effectively inhibited by brief exposure to inert gases at pressures of 5000 psig or less.