DNA typing techniques were used to examine selected clinical and environmental isolates of Sporothorix spp. recovered from the 1988 sporotrichosis epidemic in multiple states of the United States. Previous studies indicated that isolates in one of the six morphologically or physiologically distinct groups (group I) obtained from environmental sources were Sporothrix schenckii and were the possible etiologic agents responsible for the epidemic. To assess this hypothesis at the genetic level, whole-cell DNA was extracted from selected clinical isolates and representative members of each of the six environmental groups subjected to endonuclease digestion and then analyzed by gel electrophresis. DNA types were assigned on the basis of restriction fragment length polymorphism patterns. One DNA type was common to clinical and group I isolates but was dissimilar from the DNA types exhibited by groups II to VI. In contrast, a variety of DNA types were associated with isolates in groups II to VI. The latter groups appeared to make up a heterogeneous collection of fungi, with some members of the same group having different DNA types but with others from different groups possessing identical DNA types. Thus, DNA typing studies confirmed that group I environmental isolates are indistinguishable from clinical isolates and that group II to VI isolates represent a complex of related fungi with similar Sporothrix anamorphs.