Kinetics of the spontaneous decarboxylation of 6-nitrobenzisoxazole-3-carboxylic acid have been studied in the lyophases formed by anionic, cationic and nonionic surfactants : sodium dodecyl sulfate (SDS), myristyltrimethylammonium bromide (MTAB) and pentaethylene glycol mono-n-dodecylether (C12E5) respectively. This substrate was chosen for study because of the large amount of data available on its behavior in micellar solution. Without surfactants the reaction proceeds slowly in both acidic (pH 4.0) and alkaline (pH 9.0-11.0) water solutions, with the reaction rate similar to 0.7 x 10(-5) s(-1) (at 25 degrees C). Anionic SDS has no catalyzing effect on the reaction. Cationic MTAB significantly accelerates the reaction in all phases : isotropic, lamellar or cylindrical nematic. Nonionic C12E5 is the only surfactant which shows a catalyzing effect dependent on the type of the lyophase. The reaction goes similar to 1.5 times faster in the lamellar as compared to the isotropic phase.