Semiconductors form the backbone of all modern-day microelectronic and optoelectronic devices. These devices get exposed to various types of radiation when they are used in radiation environments. Exposure to radiation can cause degradation to the performance of these devises leading to their failure. Therefore, it is necessary to evaluate the performance of semiconductor devices under radiation environments. This monograph deals with an experimental study on the effect of 8 MeV electron irradiation on single crystalline Silicon and polycrystalline thin film Cadmium Telluride (CdTe) devices. A brief introduction to the subject is followed by experimental techniques used. Results of the studies on the effect of electron irradiation on Silicon and CdTe Schottky diodes, Silicon Photo-detectors and CdTe Solar Cells have been discussed and the radiation tolerance of single crystalline Silicon and polycrystalline CdTe thin film have been compared. This is specially targeted to researchers working in the field of irradiation effect on semiconductor devices as well as postgraduate students of Physics, Electrical and Materials Engineering.