Use of hormones for fattening purposes is forbidden in the animal production in Europe (European Commission. 1996. Council Directive EC/96/22 (replacement of 88/146/EC). Off J Eur Commun. L125:3–9; European Commission. 1996. Council Directive EC/96/23. Off J Eur Commun. L125:10–32). Moreover, Regulation (EC) 178/2002 (European Commission. 2002. Regulation EC No 178/2002. Off J Eur Commun. L31:1–24) and Regulation (EC) 882/2004 (European Commission. 2004. Regulation EC No 882/2004. Off J Eur Commun. L165:1–135) oblige the member states to identify emerging risks and use validated and accredited methods for control analysis. Only combinations of bioassay activity screening with chemical identification are suited to uphold all laws. No such combination is described for the detection of (gluco)corticoids. In the present study, the GR-CALUX bioassay was validated as a qualitative screening method for the determination of glucocorticoid activity in feed. This validation was performed according to EC Decision 2002/657/EC (European Commission. 2002. Commission Decision 2002/657/EC from Directive 96/23. Off J Eur Commun. L221:8–36). Twenty-two representative blank feed samples were selected and spiked with 50¿ng¿g-1 of dexamethasone, 100¿ng¿g-1 of betamethasone or 500¿ng¿g-1 of triamcinolone. All blank and spiked feed samples fulfilled the CCa and CCß criteria; the method was specific and robust and glucocorticoids in feed were stable for at least 88 days.