Unlike other boletes, all members of Gomphidiaceae (except for Gomphogaster) are agarics, having gills instead of pores.

Nonetheless, many of the microscopic features of these fungi, such as spore shape, strongly suggested an affinity with Boletales.

This was later confirmed through molecular phylogenetic investigation, which demonstrated that Gomphidiaceae are more closely related to boletes than the "true" agarics of the Agaricales and that the development of gills in this group was an independent evolutionary event from the development of gills in the Agaricales.

[4] This family of fungi has been thought to be ectomycorrhizal, forming symbiotic relationship with their host trees, however, there is now evidence that many (and perhaps all) species in this group are parasitic upon ectomycorrhizal boletes, in relationships that are often highly species-specific.

[5][6] "The Gomphidiaceae revisited: a worldwide perspective" by Orson K. Miller, Jr, Mycologia 95(1):176–183, January/February 2003.