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 ??/kg to 3000 ??/kg and in wheat flour in the range of 2@5 ??/kg to 100 ??/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 ??/kg to 50 ??/kg.