The present paper is a preliminary report on a quantitative study of the foraminiferal contents of Late- and Post-Glacial clay samples from the Oslofjord area. It appears that sediments of Late-Glacial and Post-Glacial age are sharply defined by a few dominent species in their foraminiferal faunas. A subdivision can be based partly on the dominance of some species and partly on the presence of certain accessory species. In this way, most samples from the area could be rapidly placed in the old stratigraphic scheme based on megafossils.