A new high-performance liquid (HPLC) chromatographic method is described for cyclopiazonic acid (CPA) determination in fungal cultures on a propylamino-bonded stationary phase with a CH CN/CH COONH buffer as mobile phase. 3 3 4 Retention of CPA on propylamino modified silica under acidic conditions (protonated amino groups and deprotonated CPA) is governed by a mixed ion-exchange-reversed-phase mechanism. In addition to non-polar (hydrophobic) interactions, polar interactions with the surface silanols are also possible and become important as the polarity of the mobile phase decreases. A detection limit of 25 pg of CPA standard is obtained that represents an improvement of more than two orders of magnitude compared to existing HPLC procedures. UV-detector response was linear to 200 ng of CPA. Fungal extracts can be analysed after a simple dilution step with UV diode array detection that provides peak identity / purity assessment. The suitability of the proposed method as a rapid confirmatory test to assess the toxigenic potential of different Aspergillus and Penicillium strains is demonstrated by the analysis of 54 fungal extracts. Ó 2002 Elsevier Science B.V. All rights reserved.