Kinetics of oxidation of L-cysteine by penta-coordinated Co (III), Fe(III), and Cr(III) complexes ofsalicylaldiminato ligands have been studied in aqueous solutions. Metal complexes of Nsalicylidinecyclohexylamine,N-salicylidinisopropylaniline, N-salicylidinnaphthylamine, N-(4-sulfonitsalicylidine) cyclohexylamine, and N-(4-sulfonatesalicylidine) -2-isoprpylaniline were usedin the studies. Measurements were run at constant temperature (25º C), constant ionic strength(0.20 M), and constant pH (7.0) under pseudo-first order conditions, in which the concentrationof cysteine is around two orders of magnitude greater than that of metal complex. The observedrate constant was determined by following the change in absorbance of reaction mixture at apredetermined wavelength with time. Results show that the rate of oxidation depends on stericfactor and the electron withdrawing / releasing ability of the ligand bound to the metal ion. It alsodepends on the metal center. The Co(III) complexes were found to have the highest rates due tohigher reduction potential of Co(III).