The quantitative treatment of metallomicellar catalysis involving a ternary complex containing ligand, metal ion, and substrate is proposed in this paper. The catalysis of the cleavage of p-nitrophenyl picolinate (PNPP) by the Cu2+-coordinatingN-myristoyl-N- (beta-hydroxyethyl)ethylenediamine in CTAB micelles was studied in aqueous buffer of pH ranging from 5.0 to 7.0 at 25 degrees C. The effect of pH on the reactivity is discussed. The result indicates that the 1:1 complex of the ligand and CU2+ is an active nucleophile in 0.01 mol.dm(-3) CTAB micellar solution. The pK(a) of the hydroxyl group of the ternary complex was determined to be 6.52 in aqueous CTAB micelles. The rate constant, which shows the nucleophilic reactivity of ionized hydroxyl anion of the ternary complex toward PNPP, was determined to be k(Nmax) = 0.625 s(-1).