Glass and polycrystalline materials for high-level radioactive waste immobilization are discussed. Borosilicate glass has been selected as the waste form for defence high-level radwaste in the US. Since release of the radionuclides to the biosphere is the major concern, this paper focuses on the potential interactions between the waste form and its surroundings. In addition to laboratory data, results from field testing are also presented in order to provide a comprehensive overview of glass leaching under near repository-like conditions.