Three murine monoclonal antibodies (Mabs) were raised against a cytoplasmic antigen of the yeast phase of the pathogenic fungus Sporothrix schenckii using a modification of standard hybridoma technology incorporating the immunosuppressive drug cyclophosphamide. When tested for species-specificity within the pathogenic dimorphic fungi one of these Mabs (S5) showed little cross-reactivity by enzyme-linked immunosorbent assay and Western blot, though there was some recognition of Paracoccidioides brasiliensis antigen. This Mab recognized a 70-75 kDa molecule on reduced Western blots of S. schenckii antigen. The other two Mabs (S12 and S15) showed cross-reactivity with all dimorphic fungal antigens tested, though they appeared to recognize a molecule of similar molecular weight. This is the first report of any attempt to raise species-specific Mabs against this important causative agent of dermatological disease.