The objective of the present revision is to complement the lithostratigraphy of the Ieper Group published in 2001 (Laga et al., 2001). This last publication reflected the activities in the Tertiary Subcommission at that time. The review published in 2001 framed in an initiative of the National Stratigraphic Commission and was limited to the lithostratigraphy at formation level. The Laga et al (2001) reference document has been the basis for the NCS website until now. The Ieper Group is characterised by clay−dominated sediments overlying, in most situations, the Landen Group strata and, if not outcropping, underlying the sand−dominated Zenne Group sediments. According to Laga et al. (2001) in their reference document for Paleogene and Neogene lithostratigraphy, the Ieper Group consists of the Kortrijk, Tielt and Gentbrugge Formations and ,members in these Formations are only listed. These subdivisions are also used on the 1:50 000 geological maps of Flanders, edited in the last decades of the 20th century. Especially the additional description of the members, and where possible, horizons, identified in the Formations, made the present review necessary and also modifications at the formation level itself arisen since 2001 needed to be integrated in a new synthesis. The present update is based on the earlier description of members in Maréchal & Laga (1988), Geets et al. (2000) and Steurbaut (1998) as far as appropriate. All modifications, discussions and additions are supported by the relevant literature references.