The effect of added surfactants, sodium dodecylsulfate (SDS), Triton X-100 (C8Hl7C6H4(OCH2CH2)xOH, x = 9, 10), and cetyltrimethylammonium bromide (CTAB), on measured rate constants for electron transfer between Co(terpy)2(2+) and a series of cobalt(III) complexes, [Co(phen)3]3+, [Co(5-Cl-phen)3]3+, [Co(5-Me-phen)3]3+, [Co(5,6-Me2-phen)3]3+, [CO(5-SO3-phen)3], and [Co(dipic)2]-, varying in ligand structure and ionic charge, have been determined by stopped-flow spectrophotometry. The observed rate catalysis or inhibition, resulting from micellar interactions, has been rationalized using the Berezin model. Information on micellar binding, afforded by the kinetic data, correlates with electrochemical changes, particularly changes in anodic and cathodic peak currents and half-wave potentials, determined by cyclic voltammetry, that result on addition of surfactant solutions to the cobalt complexes. Strong hydrophobic interactions dominate the micellar binding of divalent cationic terpyridine and phenanthroline complexes with SDS micelles, and the enhanced stabilization of the reduced state in the micellar environment is reflected in the magnitude of the observed potential shifts. The presence of the polar SO3- substituent in the neutral sulfonated cobalt(III) phenanthroline complex inhibits its association with anionic SDS. Potential shifts for the anionic Co(dipic)2 complex in Triton X-100 and CTAB also appear to reflect changes in the relative stability of oxidation states in the surfactant media.