The stable configurations of hydrogen in undoped, and inn- andp-semiconductors are reviewed. We compare the experimentally determined configurations with theoretical predictions made by a variety of calculational methods. In undoped Si, as an example, hydrogen appears to occupy a energy occurring at a tetrahedral interstitial (T) site. In B-doped,p-type Si, hydrogen at a near BC site accounts for acceptor passivation. By contrast inn-type Si, hydrogen at the antibonding (AB) position appears to be responsible for donor passivation. The possible configurations in other semiconductors (Ge, GaAs and AlGaAs) are also summarized.