Life cycle impact assessment (LCIA) developments are explained along with key publications which record discussions which comprised ISO 14042 and SETAC document development, UNEP SETAC Life Cycle Initiative research, and research from public and private research institutions. It is recognized that the short list of impact categories has remained fairly constant, even after extensive discussions. The termination point of impact assessment modeling (e.g., inventory, midpoint, endpoint, damage, single score) has been discussed extensively, and the advantages and disadvantages of these different levels are well published. Early LCIAs were conducted independent of system location, but now site-specificity has been a research topic for many of the local and regional categories (e.g., acidification, eutrophication, and smog formation). In reality, even though many advances have been made in site-specific analysis, the life cycle assessment (LCA) case studies are often limited to their inventory data, and as a result, most LCAs are still site-generic even though the LCIA methodologies exist to allow for site-specific analysis. Pollutant-based impacts have received the most research effort and support in the past, but resource depletion categories (e.g., land use and water use) are now recognized as being highly complex, site-specific, data intensive, and important for contributing toward the sustainability of the planet. Efforts in these categories are still in the neophyte stages and are expected to have the greatest advances in the upcoming years.