Relationships between the hemiparasite Rhinanthus serotinus (Schonh.) Oborny and some environmental variables have been compared to those of some other species. The ecological response curves show that Rh. serotinus is not strongly influenced by spatial variation of macro-nutrients (nitrogen, phosphate and potassium). The species is absent on relatively wet spots, possibly due to effects of inundation. The wide amplitudes with respect to nutrients and the relatively low sensitivity to drought are probably the result of its hemiparasitic behaviour and the large number of potential hosts. A multivariate analysis of vegetation records demonstrated Rh. serotinus to be indicative for a stage in a secondary succession series of hayfield vegetation after termination of agricultural management. The structure of vegetation appears to be related to the quantity of Rh. serotinus within a community.