Electrical conductivity and Hall effect measurements are performed on solar grade bulk polycrystalline silicon of grain size ≈ 1 mm in the temperature range 85 to 550 K. The mobility is found to vary as ∼ T−2.2 above 250 K characteristic of lattice scattering. The low temperature behaviour of mobility indicates both, lattice scattering and grain boundary scattering operating simultaneously and limiting the conduction process, when the barrier height is small and grain size is large. Assuming the situation within the grain to be like a single crystal, a grain boundary barrier height of 0.023 eV is obtained from the effective mobility values. The trap state density is calculated to be 2.5 × 1012 cm−2 using a localised state model. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA