Evidence is presented which demonstrates that titanium dioxide does in fact photogenerate H2O2 in the presence of the donor sodium formate. However, this H2O2 has only a transient existence in aqueous dispersions. This was confirmed by experiments in which H2O2 was injected into the dispersion. The reasons for the lability of H2O2 are discussed and possible mechanisms presented. Electron paramagnetic resonance experiments using spin traps reveal that photolysis of TiO2 dispersion generates •OH radicals in the donor-free case while •CO2 radicals are observed in the presence of formate. These results are also consistent with H2O2 generation.