Theoretical and experimental investigations have been made on the galvanomagnetic properties in very thin single‐crystal InSb (4.6–26.4 &mgr; in thickness) at room temperature, ranging from Ohmic to high‐electric‐field regions. Two kinds of surface are prepared by chemical etching and mechanical lapping. A transverse magnetic field of up to 15 kG is applied parallel to the surface of the samples to deflect intrinsic electrons and holes to one of the surfaces. The thin sample shows a small magnetoresistance in the Ohmic region, a linear electric field dependence of the conductance in a small electric field, and a current saturation in a high electric field. From these phenomena, bulk lifetimes and surface recombination velocities are estimated. It is shown that the bulk lifetimes and the saturation current can be explained by the Auger process. Surface recombination velocity of about 104cm/sec for etched surfaces and of the order of 105cm/sec for lapped surfaces are obtained. Theoretical calculations include the case of an intermediate magnetic field which is important for InSb at room temperature.