Theoretical aspects of the kinetics of interaction of enzymes with lipid substrates are presented. Rate equations were written and used to simulate v versus S curves for interaction of enzymes with "monomers" (i.e. a molecular solution) or micelles (aggregated form) of the "soluble", amphiphilic lipids. The rate equations were written assuming separate kinetic parameters for the interaction of the enzyme with these two forms. Although the rate equations are based on the kinetic theory of Michaelis and Menten, most of the simulated v vs. S curves were not hyperbolic. A procedure is suggested for determining the kinetic parameters with the aid of a graphic method.