The electrical conductivity and the Hall coefficient of InSb single crystal specimens with real surfaces have been measured as a function of thickness and magnetic induction at various temperatures. A two conductor three band model is proposed for interpreting the experimental results. The mobilities and the carrier concentrations in the semiconductor bulk are obtained from measurements of the galvanomagnetic properties at high sample thickness. The galvanomagnetic properties of the semiconductor surface are derived from comparison between theoretical and experimental curves.