Chemiluminescence (CL) reactions were studied in a model system based on a phase diagram which was composed of Triton X-100, a-butanol, toluene, and water. The CL reaction was achieved by using trichlorophenyl oxalate, H2O2, and perylene as the fluorophore. The intensity of light (l(0)) and t(1/2) were found to depend on both reactant concentrations and phase composition. The CL reaction was conducted in W/O microemulsions, and an inverse relation between I-0 and t(1/2) was found. These two parameters could also indicate the transition from a W/O emulsion to a W/O microemulsion. The effect of medium polarity was evaluated by fluorescence, absorbance, and chemiluminescence spectra.