Photoisomerization of trans-stilbene (TS) was investigated in sodium dodecyl sulfate (SDS)/benzyl alcohol (BA)/H2O systems in order to establish the relationship between the reaction yields and the compositions and structures of molecular organized assemblies. The results show that, in SDS/BA/H2O systems with the structures of oil in water microemulsions, bicontinuous microemulsions, and hexagonal liquid crystals, the reaction yields are much larger than those in benzyl alcohol, both with and without the photosensitizer 9,10-anthracenedicarbonitrile. However, SDS/BA/H2O water in oil microemulsion and lamellar liquid crystal can obviously catalyze the photoisomerization of TS only when the photosensitizer is not present. The yield is increased with the increase in H2O content or with the decrease in BA content. (C) 2004 Elsevier Inc. All rights reserved.