Samples from 15 populations of Rhinanthus serotinus (SCHÖNH.) OBORNY were investigated in landscape Värmland in western Sweden. About 30 different characters were measured on each individual. The aim of the study was to examine the variation in morphological characters between populations and to find out whether intraspecific groups could be discerned. Through statistical analysis it was concluded that it was possible to divide the material in three groups corresponding to var. vernalis, var. aestivalis and var. serotinus. The least variable character for each variety was "number of internodes" which accordingly was regarded as the most important for variety delimitation. This character is closely correlated to flowering time, showing the adaptation to different habitats. The early flowering taxon, var. vernalis, is connected with meadows used for haymaking while the latter two occupies more varying habitats, e.g. road verges and ditches.