As a consequence of the finding of veterinarian drugs in food European Community banned several compounds like coccidiostats as amprolium (APL). This antibiotic has been used as a preventive and clinical anticoccidial drug in chicken. The 2005/187/CE, 2005/925/EC Recommendations ban the use of amprolium as additive in chicken feed. For this reason a rapid and sensitive liquid chromatography–mass spectrometry (LC–MS) method was developed to detect amprolium in chicken feed following the European community proposed technique (1999/27/EC) for sample preparation. Cause the validation is required for the analytical methods used in feed official control, this method was validated according to 2004/882/EC Regulation.