A derivative of resorcinylic acid, produced by the fungus Fusarium graminearum, has been found to be responsible for the estrogenic signs in swine and laboratory rats. An estrogenic response in rats can be incited by injecting intramuscularly as little as 20 mug of the estrogen (F-2). Stimulation in growth of rats was noted at the lower concentrations (20 to 40 mug) of a series. Up to 3,500 ppm of the estrogen was produced on a solid corn medium. The compound is relatively stable to heat and ultraviolet irradiation. Methods of analysis have been developed and include: extraction procedures, evaluations by ultraviolet absorption spectrophotometry, thin-layer chromatography, and gas-liquid chromatography.