Feeding continuously operated stirred tank reactors with reactants and homogeneous catalysts subject to inactivation will usually lead to a limited substrate conversion with increasing space time. However, it is shown that a max. of conversion may be obsd. under certain circumstances. Guided by exptl. evidence, the theor. background is discussed for identifying reaction systems for which such conversion maxima at distinct space times may be obtained. This phenomenon may be obsd. only if the catalyst undergoes deactivation characterized by kinetics of less than 1st order. Therefore, a likely case for exptl. verification consists in an enzyme reaction accompanied by proteolytic degrdn. of the substrate-transforming enzyme due to the presence of a protease. [on SciFinder (R)]