Zilpaterol is a new powerful beta-agonist, which is officially registered for fattening purposes in cattle in Mexico and South Africa. Its chemical structure is different from the well-known beta-agonists. Therefore, the routinely used screening methods are not likely to be suited for the analysis of zilpaterol. Also gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry (LC-MS) methods need to be adapted to enable detection of zilpaterol. In this study, a LC-MS3 confirmatory method was developed for the simultaneous detection of zilpaterol and di-aromatic beta-agonists in urine samples. A LC-MS2 method was optimised for the detection of zilpaterol in faeces. To study the excretion profile in urine and faeces, a male veal calf was orally treated with daily doses of Zilmax ® during 2 weeks. Zilpaterol was mainly excreted via urine. © 2004 Elsevier B.V. All rights reserved.