In his recent paper "Rectification in heavily doped p-type GaAs/AlAs heterojunctions" [J. Appl. Phys. 70, 1081 (1991)] Yoffe presented calculations of barrier heights and current-voltage characteristics. Unfortunately, he adopted a typographical error in his basic equations. In this comment we show that significant differences in barrier heights and currents across heterojunctions arise, using the corrected expression for the calculations.