Using InGaAs for the base and InAlAs for the emitter and collector barriers, we have fabricated the first hot‐electron transistor in this material system. We have shown that 1.6% of the injected hot electrons can be transported ballistically through a 0.3‐&mgr;m‐thick In0.53Ga0.47As plus 800‐A˚‐thick InAlAs barrier layer at 77 K giving rise to an average mean free path of 920 A˚. An energy spread of 130 meV was observed for the ballistic electrons injected at about 700 meV above the thermal equilibrium conditions. The values of collector barrier heights measured are in reasonable agreement with those deduced independently from thermionic emission studies in InGaAs gate, InAlAs/InGaAs capacitor structures.