The current status of research and development on titanium oxide based visible and UV (ultraviolet) light photocatalysts is presented including a discussion of the physical-chemical effects of different dopants. Progress made in the past decade has triggered the development of several marketable applications. In particular, the state of the art of products for indoor and outdoor applications and challenges related to their introduction on the mass market are illustrated. Future trends in technology and market perspectives of photocatalysts are discussed in terms of performance improvement and materials process development. (C) 2008 Published by Elsevier B.V.