A new, fast and efficient multiple reaction monitoring (MRM) high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the determination of cyclopiazonic acid (CPA) in mixed feed, wheat, peanuts and rice is presented. The analytical methodology involves sample extraction with an alkaline methanol-water mixture, defatting with hexane and quantification using HPLC-MS/MS without further treatment of sample extracts. Reversed-phase liquid chromatography using a C18 stationary phase coupled to negative mode electrospray triple quadrupole tandem mass spectrometry was applied. The limit of detection was 5 microg/kg while the limit of quantification was 20 microg/kg in the matrices investigated. The detector response was found to be linear over the range 25-250 microg/kg in feed and 25-500 microg/kg in wheat, peanuts and rice. The mean overall recoveries (n=18) of CPA varied from 79% to 114% in the range of concentrations studied over a period of 4 months. Mean recoveries (n=3 or 6) of CPA in wheat, peanuts and rice varied from 70% to 111%, 77% to 116% and 69% to 92%, respectively. The method was successfully applied to the analysis of feed and rice samples artificially infected with the fungal strain Penicillium commune, where the toxin was found at different levels.