A monoclonal antibody, McAb-ST, specific for sterigmatocystin (ST) was produced in vitro and in vivo by a hybridoma anti-ST1. Anti-ST1 was prepared by fusion of SP2/0 murine myeloma cells with spleen cells isolated from BALB/c mouse that had been immunized with a complete antigen BSA-ST (ST conjugated to bovine serum albumin). Analysis revealed that McAb-ST was of the IgG1 type, the molecular weight of McAb-ST was 168,000 daltons (53,000 for each heavy chain, 31,000 for each light chain), and the apparent affinity constant of McAb-ST with H-ST (Hemocyanin and ST conjugate) was 1.29 x 10(9) mol/L. The relative cross reactivities of McAb-ST with ST analogs were less than 2% when determined by a competitive indirect enzyme-linked immunosorbent assay (CI-ELISA). The minimal 0.5 pg of ST in 50 microliters of solution could be detected with CI-ELISA using McAb-ST, with a linear range of 0.1-10 ng/mL.