We have prepared a number of GaAs structures d-doped by Sn using the well known molecular beam epitaxy growth technique. The samples obtained for a wide range of Sn doping densities were characterized by magnetotransport experiments at low temperatures and in high magnetic fields up to 38 T. Hall-effect and Shubnikov-de Haas measurements show that the electron densities reached are higher than for other d dopants, like Si and Be. The maximum carrier density determined by the Hall effect equals 8.4 × 1013 cm-2. For all samples several Shubnikov-de Haas frequencies were observed, indicating the population of multiple subbands. The depopulation fields of the subbands were determined by measuring the magnetoresistance with the magnetic field in the plane of the d-layer. The experimental results are in good agreement with selfconsistent bandstructure calculations. This calculation shows that in the sample with the highest electron density also the conduction band at the L point is populated.