The growth and properties of AlGaN/GaN heterojunction bipolar transistors grown by low-pressure metalorganic chemical vapor deposition (MOCVD) are described. The "emitter-up" structures are grown on (0 0 0 1) sapphire substrates, Common-emitter characteristics and Gummel plots were measured on 120 x 120 mum(2) devices and useable DC current gains of beta similar to 8-14 were achieved at room temperature. The resistance of the base was a limiting factor in high-current operation of these devices.