Application of supercritical fluids and liquid gases as an alternative reaction medium for enzyme-catalysed reactions is presented. The factors affecting the enzyme stability in supercritical fluids (effect of water activity, effect of pressure and temperature, number of pressurisation-depressurisation steps) and inhibition of enzymes are well documented with experimental results on hydrolases. An overview of our research on various types of HP enzymatic batch-stirred-tank-, continuous-packed-bed- and continuous-membrane reactors to obtain data on productivity and to evaluate the economy of the process is given. (C) 2002 Elsevier Science B.V. All rights reserved.