The family Hygrophoraceae (Basidiomycota: Agaricales) includes one genus known to be ectomycorrhizal (Hygrophorus), two genera assumed to be mycorrhizal (Humidicutis and Camarophyllus), one genus assumed to be saprotrophic (Hygrocybe), and several that lichenize with green algae and cyanobacteria (Lichenomphalia, Dictyonema, Acantholichen and others). To date, there has been no confirmation of the nutritional strategies of Humidicutis, Camarophyllus and Hygrocybe. In this study, we are combining molecular phylogenetics with analyses of stable isotopes to understand the diversity and evolution of nutritional strategies in Hygrophoraceae. The isotopic profiles of the three genera of uncertain nutritional mode are different from those of both ECM and saprotrophic fungi in other families, which, coupled with phylogenetic analysis, elucidate several changes in strategy over the course of this family's evolution.