The photocatalytic activity of WO3 semiconductor powder for water splitting into H-2 and O-2 was studied. Instead of conventional broad spectrum light sources like lamps, monochromatic laser radiations in the UV region (lambda = 355 nm) were used as the light source for the study of photocatalytic water splitting over WO3. An alternate route based upon the photo- chromic properties of WO3 for the production of hydrogen was suggested. The effect of dissolved metal ions on H-2 and O-2 yield in the presence of various metal ions was also investigated. The effect of the hole- capture agent on H-2 and O-2 yield was also studied by using methanol as a hole- capture agent. The data on pH measurements during the course of reaction was found very useful in explaining the reaction mechanism in general, and metal ions action in particular.