Abstract: Cenozoic chronostratigraphy has been an active area of research over the past 50 years. The expanding search for energy and the development of international scientific drilling have resulted in a wealth of stratigraphic data. Many issues in Cenozoic chronostratigraphy, however, remain unresolved. For example, of the 18 recognized stages within the Cenozoic, only 9 have a ratified Global Stratotype Section and Point (GSSP). Only the Pliocene Series has all of its component stages defined by GSSPs. Good progress has been made on the remaining 9 stages. Almost all have guide events identified which should serve for correlation and many have candidate sections which may serve as GSSPs. The outlook is good for the ratification of all Cenozoic GSSPs within several years but the target date of 2008 may be too optimistic. At least three other unresolved issues dealing with Cenozoic chronostratigraphy need further discussion and research. They include the status and chronostratigraphic rank of the Tertiary, the stage nomenclature at the Paleocene-Eocene boundary, and the “decapitation” of the historic Priabonian Stage. The unresolved GSSPs represent an immediate concern. The stability of correlations within the Cenozoic depends on the establishment and maintenance of GSSPs. Future work on Cenozoic Earth history will be enhanced by the completion of this task.