Radiation effects on InP-based electrical and optical devices are discussed from the standpoint of device structure and physics. The devices addressed are High Electron Mobility Transistor (HEMT), Heterojunction Bipolar Transistor (HBT), and solar cells. Radiation effects due to neutrons, gamma rays, electrons, protons, x rays, and total dose radiation can result in device parameter degradation, upset, burnout, and current leakage problems. The effects are correlated to device structure and material properties. Comparisons are made to GaAs or Si devices that have performance characteristics similar to the above-mentioned InP devices. Finally, recommendations are made for testing and modeling these effects.