Optical characterization of TIGaS2xSe2(1-x) mixed crystals have been carried out at room temperature using the transmission and reflection measurements in the wavelength range of 400-1100 nm. The spectral dependence of the refractive index for all compositions of studied crystals were obtained. The dispersion of the refractive index is discussed in terms of the Wemple-DiDomenico single-effective-oscillator model. The compositional dependencies of refractive index dispersion parameters: oscillator energy, dispersion energy and zero-frequency refractive index were revealed. (c) 2012 Elsevier B.V. All rights reserved.