Because inappropriate prescribing is prevalent in individuals aged 65 and older, various criteria to assess it have been developed. This study's aim was to systematically review articles that describe criteria for assessing inappropriate prescribing in individuals aged 65 and older and to define the circumstances of their use (explicit/implicit), origins, development processes, and content. A systematic search was conducted on MEDLINE and PubMed (1990–2010) and augmented with a manual search. Original articles written in English were included if they described the development of the criteria and were aimed at people aged 65 and older. Articles that described criteria applicable only in hospital settings, specific drugs, or a particular disease or condition were excluded. Sixteen of 535 articles met the inclusion criteria. They described 14 criteria, half originating in the United States. The English-language restriction limited the search results. Most criteria were explicit, consensus validated, based totally or partly on Beers criteria, and focused on pharmacological appropriateness of prescribing and some were old. Drug- and disease-oriented explicit criteria require regular updating and are country specific. Implicit, person-specific criteria are universal and do not need updating, although their use requires up-to-date professional skills. Unlike explicit criteria, implicit criteria have been validated in people. Some of the 14 criteria were noncomprehensive, mainly because of the intended purpose. To conclude, different criteria exist for optimizing prescribing for individuals aged 65 and older. Possible deficiencies must be recognized and trade-offs made when selecting criteria for use. In the future, more-comprehensive and -timely criteria are needed.