The photoassisted degradation of phenyltin(IV) chlorides in air-equilibrated aqueous TiO2 suspension has been studied. The stability of the triphenyltin(IV) derivative in aqueous solutions at different pH values and the extent of adsorption of tri- and diphenyltin(IV) chloride species were examined. Particular interest is focused on the TiO2-assisted photodegradation of phenyltin species. Detailed surface analyses of the catalyst particles by IR and of the liquid medium by GC-MS are reported. A mechanism consisting of interfacial trapping of a photogenerated electron-hole pair can explain the TiO2-photoassisted degradation of phenyltin species. The results are compared with those previously reported on the photolytic degradation of theses species in water and with those of n-butyltin species (photolytic and TiO2-photoassisted). Our results allow that this is not a photocatalysis system but a photoassisted one in the presence of TiO2.