We present the current–voltage characteristics of a T‐shaped semiconductor electron waveguide structure in the nonlinear regime. This system is interesting as a potential quantum interference transistor. Calculated zero‐temperatureI–Vcharacteristics are with multiple peaks and exhibit regions of negative‐differential resistance. The peak‐to‐valley ratio has maximum value of 3:1. The calculated values of the transconductance and the differential drain conductance are small, which suggests limited abilities for conventional applications of the transistor. ©1996 American Institute of Physics.