Bismuth thin films of various thicknesses in the range 150-3500 Å have been vacuum deposited on clean glass substrates held at room temperature. Resistances were measured both before and after heat treatment in situ, which was carried out immediately after film formation. It is found that the resistivity oscillates with thickness both for unannealed and annealed films. The same kind of oscillatory behaviour with thickness is also observed in the case of defect resistivity. It is argued that the above oscillatory behaviour is due to the oscillatory behaviour of mobility with thickness. It has also been pointed out that the mobility due to scattering by point defect clusters also oscillates with thickness, if the range of the scattering potential is taken to be of the order of the linear dimensions of the clusters. © 1979 Pergamon Press Ltd.