The current voltage relationships of AlGaAs/GaAs modulation doped field effect transistors (MODFETs) were measured as a function of applied uniaxial stress. Stresses in the [110] and [11¯0] directions on MODFETs that were grown on a (001) substrate produced threshold shifts of opposite sign. Stresses in [110] and [11¯0] directions resulted in threshold voltage pressure coefficients of −15 and 64 mV/Kbar, respectively. The asymmetric shifts in the threshold voltages are attributed to piezoelectric effects. In addition, stress induced changes in the slopes of the transconductance versus gate-to-source voltage relationships were also measured. For stresses in the [110] and [11¯0] directions, the dependencies were 0.4 and −0.7 mS/(VKbar), respectively.©1997 American Institute of Physics.