The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) and N-cetylpyridinium bromide (CPB) on the interaction of L-leucine and L-phenylalanine with ninhydrin have been studied at 70 degrees C, Both surfactants strongly catalyze the reactions. The reaction rates are higher in CTAB micelles than in CPB micelles. Quantitative kinetic analysis has been performed on the basis of a pseudo-phase model. The influence of different salts on the reaction rates has also been seen and it is found that tightly bound/incorporated counterions are the most effective.