ABSTRACT: The latest Oligocene and early Miocene diatom biostratigraphy (24.4 to 16.9 Ma) of equatorial Pacific ODP Site 199-1219 is documented and tied to paleomagnetic stratigraphy in 69 samples, allowing an average age resolution of about 100 kyrs. An updated taxonomy is provided and most of the 71 taxa are illustrated in 9 photographic plates. The equatorial Pacific diatom zonation for the latest Oligocene and early Miocene is updated: the Nitzschia maleinterpretaria Partial Range Zone is newly proposed to replace the Triceratium pileus Interval Zone and part of the Craspedodiscus elegans Partial Range Zone, and the C. elegans Zone is modified to be an interval zone. Absolute ages of 62 datum levels are estimated and compared with age estimates from elsewhere in the equatorial Pacific, as well as from the North Pacific and Southern Ocean. It is likely that many of these datum levels will be useful for correlations between the equatorial Pacific and higher latitude regions.