The surface charge carrier transport of electrons in accumulation mode insulated gate FET’s fabricated on [100] oriented samples of semi‐insulating InP has been investigated, both as a function of surface and dielectric preparation as well as of temperature over the range of 85 to 300 K. Results of these studies indicate that room temperature field‐effect mobilities as large as 4200 cm2/V s and effective mobilities of 3300 cm2/V s can be achieved in the linear region on material whose bulk Hall mobility does not exceed 3000 cm2/V s.