A systematic experimental study shows that the Hall mobilities of electrons at 77 K over the entire accessible range of electron densities in VPE GaAs films grown under high‐purity conditions are below the theoretically predicted values. At a given electron concentration the experimental mobilities are independent of the preparation parameters (As/Ga ratio, dopant element, dopant pressure, growth temperature). Most of the literature data, not only on VPE but also on LPE and MBE films, appear to be in good agreement with these results. This finding casts some doubt on the idea that all such layers are electrically compensated.