N-Methylhydroxystilbazolium bromide was photolyzed in aqueous and nonaqueous AOT lyotropic liquid crystalline systems and in isooctane-based inverted AOT micelles or microemulsions. A competition between trans --> cis photoisomerization and photodimerization was found, the latter prevailing in systems with bent interfaces. The AOT-glycerol phase diagram was measured. It exhibits a lamellar phase at between 35 and 75% AOT w/w and an inverted hexagonal phase at >85% AOT. The clearing temperatures TLI and T-iHI (as observed in phase transitions from the lamellar lyotropic liquid crystalline phase or from the inverted hexagonal phase to the isotropic micellar phase of AOT-glycerol and AOT-water-decane systems) were found to be sensitive to the presence of small amounts of three N-alkylhydroxystilbazolium bromides. The influence of T-LI and T-iHI is specific for the stilbazolium salt and depends on its concentration and its degree of photoconversion. Thus phase transitions can be induced isothermally by irradiating samples at temperatures close to the transition temperatures.