Raw cow's milk collected from dairy farms in the province of Leon, Spain, was examined for aflatoxin M(1) (AFM(1)). The samples were analysed with a commercial competitive enzyme-linked immunosorbent assay (ELISA) kit and high-performance liquid chromatography (HPLC). The concentrations of AFM(1) in the milk extracts were initially estimated by ELISA, with recovery rates of 74.6-109% for artificially contaminated milk at levels of 10-80 ng x l(1). Samples found to contain more than 10 ng x l(1) were further quantified with HPLC. The mean recovery for this method was 89.3%. The quantification limit was 10 ng x l(1) for both ELISA and HPLC. Although AFM(1) was confirmed in only 3.3% of the samples, the concentrations in all these cases were lower than the maximum limit applicable to these products pursuant to European Union legislation. Both methods were validated with reference material certified by the Community Bureau of Reference.