A comparative study of the charge-transfer photochemistry of oxalatoammine and cis-chloro(aniline)-bis-ethylenediamine cobalt(III) complexes in pure aqueous as well as in premicellar and micellar solutions of three different surfactants (anionic, cationic and nonionic) is reported. The results indicate : (1) The quantum yield of Co2+ (φCo2+) changes as the concentration of surfactant changes with a concomitant change in the microenvironment of the probe. The manner in which φCo2+ varies, depends on the nature of the surfactant. The CMC of a surfactant can be determined from the plot of φCo2+ vs. -log[Surfactant]. (2) The photoaquation of ammonia in the complex does not take place in micellar solutions of SDS and CTAB but occurs to a small extent in micellar solution of Triton X-100. The photolysis of the oxalatoammine Co(III) and cis-chloro (aniline)-bis-ethylenediamineCo(III) complexes has also been carried out in w/o microemulsions. The results reveal that the efficiency of the intramolecular photoredox process as manifested in the quantum yield, φCo2+, decreases as the size of the water pool of the microemulsion droplets decreases.