Mobility measurements have been carried out at room temperature on phosphorus‐doped silicon samples. The desired concentration of dopant, varying in the range 1019–1020atoms/cm3, was obtained in three different ways: homogeneously during growth of the crystal, by ion implantation, and by thermal diffusion. Significant differences have been observed. A theoretical analysis, based on scattering due to dopant impurities, dislocations, and point defects, has been found to be in reasonable agreement with the results obtained from mobility measurements and from transmission electron microscopy and x‐ray analysis performed on the samples.