The first section of this review (Part I) begins with a brief historical timeline for research on the bio-alteration of glass and is followed by a discussion of the two general pathways by which alteration can occur: biophysicochemical and biochemical. The second part of this review (Part II, separate publication) discusses which organisms have been identified in the literature on altered glasses and is followed by an overview of possible bio-alteration mechanisms. These manuscripts conclude with comments on how these processes can begin to be unraveled by careful analysis of naturally altered surfaces and well-designed laboratory tests. The first section of this review does not cite every paper published on the bio-alteration of glass, but focuses on manuscripts that identify the biological agents and possible mechanisms of the observed phenomena. An emphasis has been placed on the alteration of anthropogenic glasses, but data on the bio-alteration of natural glasses, predominately volcanic in origin, and select silicate minerals are included when appropriate. The bio-alteration of glasses designed for biological applications (i.e., bioglasses) is not discussed due to their vastly different alteration environment and glass chemistries.