The temperature dependence of electrical conductivity and the photoconductivity of polycrystalline Cu 2 ZnSnS 4 were investigated. It was found that at high temperatures the electrical conductivity was dominated by band conduction and nearest-neighbour hopping. However, at lower temperatures, both Mott variable-range hopping (VRH) and Efros-Shklovskii VRH were observed. The analysis of electrical transport showed high doping levels and a large compensation ratio, demonstrating large degree of disorder in Cu 2 ZnSnS 4 . Photoconductivity studies showed the presence of a persistent photoconductivity effect with decay time increasing with temperature, due to the presence of random local potential fluctuations in the Cu 2 ZnSnS 4 thin film. These random local potential fluctuations cannot be attributed to grain boundaries but to the large disorder in Cu 2 ZnSnS 4 .the CZTS absorber layer and the Mo back contact have been pointed out as factors that reduce the solar cell efficiency [4,5]. Strong research efforts have been made in the study of different CZTS synthesis routes [3][4][5][6][7][8][9][10], CZTS structural and optical properties [2,[6][7][8], as well as in the development of CZTS solar cells [3-5, 9, 10]. However, very little is known about the electrical transport and photoconductivity properties of CZTS thin films and further studies are required.The study of the temperature dependence of electrical transport in semiconductor materials is very important for the knowledge of material parameters, the understanding of the transport and microscopic mechanisms of charge transfer, as well as for the optimization and design of solar cells. Very recently, we have shown that the radiative and non-radiative recombination mechanisms in CZTS thin films are strongly