Catalysis of organic reactions by micellar aggregates in aqueous solution lacks synthetic utility in its present state, largely for two reasons: first, the selectivity attainable in a loose unstructured micelle is low, with little possibility of attaining the degree of substrate differentiation possible in enzymes, and, second, the scale of reaction is limited, since surfactant must be in large excess over reactant to avoid swamping of the catalytic effect. The discussion will cover initial attempts to overcome these drawbacks. Increased selectivity is apparent in the promotion of ester hydrolysis by micelles of asymmetric chain-functionalized surfactants. In the most favourable circumstances 3:1 discrimination in the rate of reaction of ester enantiomers may be observed. Increased scale of reaction is obtainable when polymer-linked cationic surfactants are used as insoluble catalysts, and these hold promise for various anionactivation reas are used as insoluble catalysts, and these hold promise for varous anion-activation reactions. Specific attention is given to mechanistic aspects of homogenous and heterogeneous catalysis.