Dimethylsulfoxide (DMSO) on TiO2 is subjected to thermal decomposition, producing the surface species of CH3O, HCOO and S under vacuum. The formation of CH3O and HCOO is likely originated from the transient reaction intermediate of -OCH2O-, which is formed by dissociating both the C-S and C-H bonds of DMSO. O-2 has negligible effect on the thermal decomposition rate of DMSO, but oxidizes the reaction product of S to SO4. Photodegradation of DMSO on TiO2 generates CH3O, HCOO and CH3S in the absence of O-2. However, the CH3S is further oxidized into CH3SO3 on the surface with O-2. (c) 2012 Elsevier B.V. All rights reserved.