Anabolic steroids are banned from use in food-producing animals in the EU (Council Directive 96/22/EC). To control the zero-tolerance concept a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the screening and confirmation of most of the relevant natural and synthetic estrogenic and androgenic steroids in bovine muscle was developed and validated. The method permits to confirm and quantify almost all steroids below 1 microgkg(-1). The validation was carried out according to Commission Decision 2002/657/EC, chapter 3.1.3 "alternative validation", by applying a matrix-comprehensive in-house validation concept. Decision limit CCalpha, detection capability CCbeta, recovery, repeatability, within-laboratory reproducibility and the uncertainty of measurement were calculated. Furthermore, a factorial effect analysis was carried out to identify factors that have a significant influence on the method. Factors considered to be relevant for the method in routine analysis (e.g., operator, storage duration of the extracts before measurement, different cartridge lots) were systematically varied on two levels. The factorial analysis showed that different cartridge lots and different storage durations of the extracts before measurement can exert a relevant influence on the method.