We summarize our recent results in the effects of hydrogen on defects in germanium. Two types of hydrogen-related defect states were observed. Undoped germanium crystals which were irradiated with 1.0 MeV electrons and subsequently implanted with 27 keV hydrogen exhibited two dominant electron traps atEc–0.36 eV andEc–0.41 eV. A divacancy-like defect associated with the level atEc–0.41 eV becomes more stable when the defect captures hydrogen atoms.