A method for determination of the estrogenic mycotoxins, alpha- and beta-zearalenol and zearalenone. in cereals (wheat, barley, oats, corn) is described. After extraction with ethylacetate, clean-up involved a base treatment and partition with water, derivatization was by trimethylsilylation. For quantitation and confirmation a capillary gas chromatograph combined with a selective mass detector (ion trap), working in the electron impact-mode was used. The detection limit for the complete method is 1-mu-g/kg for each of the three mycotoxins in full scan. Recoveries from spiked cereals were 82- 86%.