Formaldehyde (HCHO) was decomposed in UV-irradiated aqueous suspensions of titanium dioxide. Initial HCHO levels in the range 60-1000 ppm, a nominal TiO2 dose of 1 g/liter, and a medium-pressure Hg lamp were employed in these experiments. Chemical oxygen demand measurements of the solution before and after photocatalytic treatment revealed the mineralization of HCHO to be complete only for the lower end (<100 ppm) of the concentration range. Direct ultraviolet photolysis of HCHO also occurred, but this pathway had an initial lag unlike the photocatalytic route. In the presence of TiO2 and ultraviolet irradiation, the direct photolysis route was bypassed and the reaction proceeded dominantly by the photocatalytic route. The kinetics of the photocatalytic oxidation of HCHO were analyzed using several models. The effect of H2O2 addition to the UV/TiO2 system was also probed as well as the homogeneous ultraviolet H2O2 approach for the treatment of HCHO. The latter exhibited the fastest kinetics for the destruction of HCHO. Finally, the long-term stability and photocatalytic activity of TiO2 were monitored with two substrates, namely, HCHO and trichloroethylene in two different media : viz. pristine water and a "real-life" water sample with bicarbonate alkalinity. No degradation in the photocatalyst performance was noted over ten repeat use cycles in either case.