Colline/submontane acidic grasslands, elements of pre-industrial farming, are declining throughout Central Europe. As they correspond largely to the priority EU habitat type 6230 (Species-rich Nardus grasslands), a syntaxonomically sound delimitation is of importance. In the Rhenish Massif (Western Germany), acidic grasslands form diverse and syntaxonomically intricate vegetation patterns. We studied such grasslands in the Lahn-Dill district near Donsbach based on 292 original releves from 1987. The dataset was classified into nine clusters. The clusters were aligned with syntaxa according to the proportions of diagnostic species. Four associations (with subunits) and one community specified to alliance were distinguished (in brackets corresponding alliances and classes): Polytricho piliferiScleranthetum perennis (Hyperico perforati-Scleranthion perennis, Sedo-Scleranthetea), AiroFestucetum (Thero- Airion, Sedo-Scleranthetea), Campanulo rotundifoliae-Dianthetum deltoidis and Hypericum perforatum-Gnaphalium sylvaticum community (Violion caninae, Nardetea strictae), Arrhenatheretum elatioris ranunculetosum bulbosi (Arrhenatherion elatioris, Molinio-Arrhenatheretea). The Polytricho piliferi-Scleranthetum perennis and the Campanulo rotundifoliae-Dianthetum deltoidis, to our knowledge, are described for the first time for Germany. By NMDS ordination we detected soil fertility and soil acidity as the main drivers for vegetation differentiation followed by moisture-related variables. On average we found 37.7 vascular plant species, 4.3 bryophyte species, and 0.6 lichen species per plot which was on average 15.6 m(2) in size. Thirty-five threatened vascular plant species, two bryophyte and eight lichen species of the German Red List indicate the area's eminent conservation value. By our study, we extended the national list of syntaxa by two associations and appreciate the diverse acidic grasslands at the eastern edge of the Rhenish Massif. Grassland conservation, habitat type, Hesse, Molinio-Arrhenatheretea, Nardetea, phytosociology, Sedo-Scleranthetea, silicicolous grassland, species-rich grassland, syntaxonomy, vegetation classification, vegetation units, species richness, management, communities, assignment, releves, Plant Sciences