An attempt is made to study the dependence of the Einstein relation on carrier concentration in heavily doped compensated semiconductors with broadened tail states, both in the presence and absence of a quantizing magnetic field, taking n‐InSb as an example. It is found that, corresponding to a given free electron concentration, the broadening of the tail states modifies the Einstein relation by enhancing the diffusivity–mobility ratio in the absence of magnetic quantization while the reverse is observed in the presence of a quantizing magnetic field. Besides, the rate of decrease of the ratio with increasing magnetic field in the quantum limit is found to be independent of such broadening effects. Copyright © 1988 WILEY‐VCH Verlag GmbH & Co. KGaA