Scientific studies on photocatalysis started about two and a half decades ago.Titanium dioxide (TiO2), which is one of the most basic materials in our daily life,has emerged as an excellent photocatalyst material for environmental purification. Inthis review, current progress in the area of TiO2 photocatalysis, mainly photocatalyticair purification, sterilization and cancer therapy are discussed together with somefundamental aspects. A novel photoinduced super hydrophilic phenomenon involvingTiO2 and its applications are presented.