Nanosized titania powders were synthesized by the reverse microemulsion (water/CTAB-butanol/cyclohexane) process varying the water content in the range of 5-30 wt.%. Materials were characterized by TEM, XRD, FT-IR, DRS, BET surface area measurement. Average crystallite size, particle size and anatase to rutile ratio was correlated with the photocatalytic decomposition of 4-nitropheol and hexavalent chromium reduction. Photocatalytic activity was evaluated by varying the pH, time of reaction, catalyst amount, etc. in aqueous phase. Highest hexavalent chromium reduction and decomposition of 4-nitrophenol was observed with the titania derived from the microemulsion having 15 wt.% of water. Prepared catalysts were found to be active in presence of sunlight. (C) 2006 Elsevier B.V. All rights reserved.