Comparative morphology, mating compatibility and extracellular laccase approaches were used to provide information on infraspecific variation within geographically separated collections of Marasmius androsaceus. Collections/cultures from North America and Europe were used for these analyses. While all utilized collections belonged to one morphological species, mating compatibility crosses revealed three intersterility groups. Extracellular laccase banding patterns confirmed genetic isolation of intersterility groups I and II.