A quantitative study, based on calcareous nannofossil assemblages, has been carried out on the Pleistocene sediments recovered during DSDP Leg 86, from site 577. Site 577 is located on the SW flank of the Shatsky Rise in the NW Pacific Ocean, in 2685m water-depth, and exhibits both good recovery and well-preserved nannofossil assemblages. Most conventional Pleistocene events have been recognised; moreover, quantitative investigations allowed the collection of further data on the stratigraphic distribution of some species (Gephyrocapsa omega >4 mu m, Helicosphaera inversa, Reticulofenestra asanoi, Helicosphaera acuta), thus improving the Pleistocene biostratigraphy of the Shatsky Rise sediments. The available magnetostratigraphic data for Site 577 also allowed the proposal of age-assignments for the following events: the last occurrence of H. acuta, the beginning and end of the temporary disappearance of G. omega, the first occurrence, temporary disappearance, and last occurrence of H. inversa, and the first and last occurrences of R. asanoi.