Hall electron mobilities in Ga1−xAlxAs alloys for various compositions have been analyzed using the Matthiessen’s rule and Monte Carlo simulation technique. Both these methods provide an excellent fit to the experimental data, providing the usefulness of Matthiessen’s rule. However, the Monte Carlo method gives mobilities at 300 K which are slightly lower (<10%) than those obtained from Matthiessen’s rule. For a typical alloy composition Ga0.70Al0.30As investigated in the temperature interval 80≲T≲300 K, the maximum deviation between the two results is found to be about 14% at 100 K.