This paper presents an extensive evaluation of self-heating in microwave Heterojunction Bipolar Transistors (HBTs). In particular, DC measurements, pulse measurements and low frequency s-parameter measurements have been performed. Pulse measurements are described in detail including optimization and characterization of lumped elements. Thermal parameters have been extracted for a recursive electrothermal network that has been connected to the temperature node of HiCuM L2. Compact model simulations are verified in time and frequency domain and found to be in very good agreement for various device geometries. The accuracy of the presented approach for thermal capacitance (C-TH) extraction has been validated with low frequency y-parameters. (C) 2012 Elsevier Ltd. All rights reserved.