Ocean Drilling Program Leg 199, the first paleoceanographic leg in 30 years to target the Paleogene equatorial Pacific, had three primary objectives. First, the drilling was designed to develop modern age models and cross-calibrate biostratigraphy, magnetostratigraphy, isotope stratigraphy, and physical stratigraphy of the equatorial Pacific in order to form a chronologic framework of events. Second, specific intervals were targeted to constrain important paleoceanographic change. Three boundaries were targeted in particular: the Paleocene/Eocene (P/E) boundary, Eocene/Oligocene (E/O) boundary, and the late Oligocene and Oligocene/Miocene (O/M) boundary. Third, comprehensive time series studies were carried out on long intervals of Paleogene core to understand the long-term evolution of the equatorial Pacific, including changes in productivity, marine chemistry, temperature, and ice volume. The scientific goals were achieved through a drilling transect that crosses the position of the 56-Ma Pacific equator with an additional drill site (Site 1218) located at the 40-Ma Pacific equator.