Anatase-brookite composite nanocrystals have successfully been synthesized at 50 degreesC using a simple liquid-phase process. The photocatalytic activity of the sample for the gas-phase oxidation of CH3CHO is 5.4 times greater than that of a single-phase anatase sample with comparable crystallite size and surface area. Electron energy loss spectra suggest that this high activity results from junction between anatase and brookite crystals. (C) 2004 Elsevier Inc. All rights reserved.