In this paper, the fifth of a series, Oligocene deposits in a North-South section near the town of St.-Truiden are described. The following units were encountered: Neerrepen Sands, Atuatuca Formation, Berg Sand, Nucula Clay, Kemiel Sands, Boom Clay and so-called ‘R2d-sand’. In this section the deposits show an obvious dip in a northerly direction. The lithological characteristics of each unit are described and discussed. The Neerrepen Soil seems to be absent in this section. The lithological development of the Atuatuca Formation is strongly different from the stratotype. It contains a mollusc-fauna hitherto only known from the Tienen area. In the introduction the authors make a plea for the preservation of the name ‘Nucula Clay’ instead of ‘Kleine Spauwen Clay’ for one of the lithostratigraphical units.