Field effect and thermoelectric power measurements have been made as a function of temperature on a series of B doped amorphous silicon samples prepared by glow discharge decomposition of silane. The investigation complements an earlier one on As doped amorphous silicon prepared by the same method. Incorporation of boron leads to an increase in the density of localized states lying 0.42 eV above the valance edge. The density of surface states is less than or equal to 1.5×1011cm−2 eV.−1Electrical transport is interpreted in a two channel model, involving transport both in extended valence states and in a band of localized states associated with the B acceptors. The effect of hydrogen evolution due to thermal annealing on the localized state densities and transport processes is also investigated.