Apophysomyces elegans and Saksenaea vasiformis frequently fail to sporulate on routine media used in clinical laboratories, thus delaying or preventing their specific identification. We have developed exoantigen test reagents capable of identifying non-sporulating isolates of A. elegans and S. vasiformis. A reagent containing three specific A. elegans precipitins was produced when A. elegans antiserum was absorbed with S. vasiformis. Antigenic analyses showed that at least two serotypes of S. vasiformis exist. Only six of 10 S. vasiformis isolates studied produced bands of identity with S. vasiformis (B-2190) (serotype 1) antiserum absorbed with S. vasiformis (B-2189) (serotype 2) antigens. The remaining four isolates, however, produced bands of identity with S. vasiformis B-2189 antiserum absorbed with B-2190 antigens. Antigenic differences among the isolates of the two groups could be correlated to some extent with the morphologic differences observed, especially with respect to the size of the sporangia and sporangiospores.