The antigenic properties of 3 UV mutants of Emmonsia crescens Emmons et Jellison 1960 were compared with the original wild strain, further with other 13 E. crescens strains, with E. parva, E. brasiliensis, E. ciferrina and Chrysosporium pannorum. For this purpose the strains were used for the immunisation of 70 rabbits. The formation of specific IgM-and IgG-antibodies was examined in their blood by means of several serologic reactions, and the capability of sensitizing the organism was proved by means of skin tests. All strains stimulated the formation of specific antibodies and sensibilised the macroorganism but in various extent. The differences in the antigenic activity was found not only among the single species but also among the single strains of the same species. All three mutants of E. crescens induced the formation of the specific antibodies but weaker than the virulent strains. They elicited, however, stronger and better reliable skin reactions than the virulent strains.