New anatase photocatalysts have been prepared by a hydrothermal technique. The powders have been shown to have a high photocatalytic activity, which is believed to be derived from their high crystallinity and phase purity resulting in fewer defects that can allow pre-emptive recombination of the free electron and positive hole. Bi-phasic particles containing both the anatase and brookite phases have also been prepared, but these have much lower photocatalytic activity.