The metabolic fate of 2(RS),3-epiminosqualene (Isq.), a demonstrable inhibitor of the 2,3-oxidosqualene-lanosterol cyclase, has been studied in Gibberella fujikuroi. The fungus transforms Isq. to a tetracyclic product for which the 24(RS),25-epiminolanosterol (EL) formulation was indicated by chromatographic and spectral data. The results are consistent with the pathway: Isq.→2,3-imino-22, 23-oxidosqualene→EL.