The conductivity type conversion from p- to n-type at a critical temperature of 315 K in TlGaS2 crystals is observed through the Hall effect measurements in the temperature range of 200-350 K. The analysis of the temperature-dependent electrical resistivity, Hall coefficient and carrier concentration data reveals the extrinsic type of conduction with donor impurity levels that behave as acceptor levels when are empty. The data analysis allowed the calculation of hole and electron effective masses of 0.36m(0) and 0.23m(0), respectively. In addition, the temperature-dependent Hall mobility is found to decrease with temperature following a logarithmic slope of similar to 1.6. The Hall mobility in the n-region is limited by the electron-phonon short-range interactions scattering with an electron-phonon coupling constant of 0.21. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.