The neutron and electron radiation effects in Ill-V compound semiconductor heterostructure devices are studied in this thesis. Three types of devices investigated are AlGaAs/GaAs high electron mobility transistors (HEMTs), AlGaAs/InGaAs/GaAs heterostructure insulated gate field effect transistors (HIGFETs), and InP/InCaAs/InGaAs single heterojunction bipolar transistors (SHBTs). HEMTs and HIGFETs are primarily investigated...