The degradation of water soluble polymers, namely, polyethylene oxide) (PEO), poly(acrylic acid) (PAA), and polyvinyl pyrrolidone) (PVP), by ultraviolet (UV) and ultrasound (US) exposure in the presence of combustion solution synthesized TiO2 (CSN TiO2) was investigated, The time evolution of the molecular weight distributions (MWDs) was determined by gel permeation chromatography (GPC). A continuous distribution model based on binary scission was proposed, and the degradation rate coefficient was determined. The degradation of polymers was also investigated with combined simultaneous exposure to UV and US in the presence of CSN TiO2. The model with binary breakage and additive contribution from UV and US fits the experimental values of the number-average molecular weight but not the weight-average molecular weight and thus is not a true representation of the physical process. Therefore, a ternary fragmentation model was developed and used to fit the experimental data successfully. The increase in overall rate of degradation on the combined simultaneous exposure of ultraviolet and ultrasound is due to an increase in the number of scission products per breakage and not due to the increase in the intrinsic rate. © 2007 American Chemical Society.