Late Eocene through Quaternary unilocular calcareous foraminifers were studied in 325 samples retrieved from six Pacific ocean DSDP bathyal zone sites (173, 192, 208, 278, 305, 321). In addition, many samples from materials used by the same authors in previous works were restudied. In total 363 taxa (sp., subsp., formae), belonging to seven genera (Fissurina, Lagena, Lagenosolenia, Oolina, Parafissurina, Pseudoolina and Sipholagena) were identified. Out of these, 87 were found exclusively in the Pacific, and 80 exclusively in the Atlantic; 196 taxa were present in both oceans. Owing to the extreme scarcity of the entire group (about 5% of the total benthic foraminiferal assemblage) and to the very long ranges of its representatives, the monothalamous calcareous foraminifers are very poor stratigraphic indicators. Two faunal turnovers were recorded during the late Eocene-Quaternary interval surveyed: between the Eocene and the Oligocene, and between the middle and late Oligocene. Similarly to the entire benthic foraminiferal assemblage, the Quaternary fauna of the unilocular calcareous foraminifer of great depths originated in the Oligocene time.