This paper documents the results of detailed calcareous nannofossil biostratigraphy of Neogene and Quaternary sediments recovered at three sites (Sites 998, 999, and 1000; Fig. 1 and Table 1) during Ocean Drilling Program (ODP) Leg 165 in the Caribbean Sea (Sigurdsson et al., 1997). The objectives of this study are (1) to describe the occurrence of stratigraphically important species, (2) to determine the boundaries of nannofossil zones, and (3) to provide an age model for the sections using standard biochronologies. In addition, detailed measurements of the size of specimens of Reticulofenestra were made to clarify stratigraphic changes and interpret their biostratigraphic utility.