Results are presented of an eight year old management experiment in a wet Arrhenatherion elatioris grassland on a heavy clay soil. The treatments were different cutting dates and frequencies or N (PK) fertilizing combined with June cutting. The treatments June with or without a second cut in September or only one cut in August gave a relatively stable vegetation. Cutting in early May produced a grassy dense sward and a second cut in September stimulated, moreover, some low growing dicots. The biomass that is produced after a first cut in May or June prevents lower growing species from persisting or spreading. Cutting later than the beginning of August produces a vegetation dominated by some rougher species. The number of species increases from 52 per 100 m 2 to 55, when the vegetation is cut in May, May and September or June; never cutting caused a decrease to 38 per 100 m 2. The annual dry matter production in two cuts is 5.6 6.1 ton/ha, fertilizing increased this level with 1.0-2.0 ton. Up till now, the number of species has not diminished. The results are discussed in relation to some data on growth physiology and growth strategy of plant species. The importance of a second cut or grazing in September is demonstrated and explained. Some practical implications are given for management aimed at main~taining or regenerating this grassland type. * Nomenclature of species is according to Heukels & van Ooststroom (1975). ** Acknowledgements We are grateful to dr. ir. J. P. van den Bergh and ir. Th. A. de Boer for criticizing the manuscript and to mrs. A. H. van Rossem for translating the text. We thank all people who analysed the yearly 4000 frequency samples.