Polycrystalline ceramics and thin films of (Sn,Ti)O-2 were prepared with the aim of investigating the mass and electronic charge transport as well as the electronic structure. The re-equilibration kinetics were monitored by measuring the de electrical conductivity as a function of temperature, 850 K < T < 1050 K, and oxygen partial pressure, 10(-15) Pa < p(O-2) < 10(5) Pa. The chemical diffusion coefficient was found to be independent of p(O-2). The energy of the forbidden band gap, evaluated on the basis of optical measurements, is presented as a function of tin dioxide mole fraction. The influence of the chemical and phase composition on the microstructure, electronic and optical properties of polycrystalline ceramics and thin films of (Sn,Ti)O-2 is discussed.