This document describes a procedure for the determination of the citrinin content in food (cereals, red yeast rice (RYR)), herbs and food supplements by liquid chromatography tandem mass spectrometry (LC-MS/MS). This method has been validated for citrinin in red yeast rice and in the formulated food supplements in the range of 2,5 ¼g/kg to 3000 ¼g/kg and in wheat flour in the range of 2,5 ¼g/kg to 100 ¼g/kg. Laboratory experiences have shown that this method is also applicable to white rice, herbs such as a powder of ginkgo biloba leaves and the formulated food supplements in the range of 2,5 ¼g/kg to 50 ¼g/kg.