We review the knowledge and understanding of proton and electron irradiation-induced defects in Si, GaAs and GaInP. We describe their nature, evaluate their introduction rates, give the electronic characteristics of the defects which play the role of recombination centers and of those which play the role of compensating centers. We then briefly describe the techniques which allow to determine these characteristics and to differentiate recombination centers and compensating centers among all the created defects. Finally, we develop and illustrate the role these specific defects play on the current generated by a solar cell. (C) 2001 Elsevier Science B.V. All rights reserved.