Hall effect and sheet resistivity measurements have been performed on boron implantations in 1μmsilicon layers on sapphire (SOS), and in bulk silicon. The doses used were 1014, 1015and 1016ions/cm2, and implantation energies were 150 and 300 keV. The samples were annealed at temperatures between 300 and 800°C. As a rule the effective number of carriers in SOS was found to be about twice the number of carriers in bulk silicon. However, the mobility is lower in bulk silicon, resulting in a sheet resistivity almost the same in boron implanted SOS and bulk silicon.