The collector-emitter offset voltage V_CE,offset of heterojunction bipolar transistors (HBTS) stems mainly from the asymmetry between the emitter and collector junctions in such devices. Based on device physics, they have developed analytical models for predicting V_CE,offset of InAlAs/InGaAs and AlGaAs/GaAs single and double heterojunction bipolar transistors (SHBTS and DHBTS). Reasonable agreement is found when the present models are compared with data taken from InAlAs/InGaAs SHBTS and DHBTS grown by molecular beam epitaxy. Comparisons between the offset voltages of InAlAs/InGaAs and AlGaAs/GaAs HBTS are also included.