The conductivity, Hall effect and magnetoresistance quantities in semi-insulating undoped GaAs and Fe-doped GaAs and InP grown by the LEC technique have been measured in the temperature range 300-420 K. It is shown that mixed conductivity is present in all samples. The experimental data were analyzed using a two-band model including electron and hole transport. A good fit has been obtained self-consistently to both conductivity and mobility. The single-band parameters have been extracted from the measured data in the studied temperature range. From ln (\R-H.0\ T-3/2) and sigma vs T-1 plots, activation energies of 0.77 and 0.65 eV have also been observed for GaAs and InP, respectively. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.