A numerical taxonomic analysis of 272 specimens and strains of Leptoxyphium, Caldariomyces and Aithaloderma was undertaken. Analysis was carried out on two data sets: characters from the form of the hyphal cells, shape of conidiomata and the presence of ascospores were coded and 34 binary variables encoded for all strains; 29 living cultures of Leptoxyphium and Caldariomyces were characterized for colony morphology, micromorphology and physiological characters encoded as 168 binary variables. Cluster analysis, principal components analysis and discriminant analysis was carried out. Three main groups are identified. A group comprising mainly Aithaloderma specimens is most clearly resolved. Another group comprises a mixture of Caldariomyces and Leptoxyphium specimens. The third group comprised mainly Leptoxyphium specimens with some Aithaloderma specimens. Physiological characters provide no evidence for the separate recognition of Caldariomyces and Leptoxyphium.