The occurrence of aflatoxin M1(AFM1)in pasteurized milk and dairy products was investigated by using direct competitive enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC). The recoveries of AFM1from the samples spiked at levels between 5 and 500 pg/ml were 88.0–106.5% for pasteurized milk and 84.0–94.0% for yoghurt by ELISA. By HPLC, the recoveries were 103–120% for pasteurized milk and 87.0–93.0% for yoghurt. The limits of detection were found to be 2 pg/ml by ELISA and 10 pg/ml by HPLC. Among a total of 180 samples collected in Seoul, Korea, the incidence of AFM1in pasteurized milk, infant formula, powdered milk and yoghurt was 76, 85, 75, and 83%, respectively, with a mean concentration of 18, 46, 200, and 29 pg/g, respectively, when determined by ELISA. These results obtained by ELISA were closely related to those by HPLC for AFM1(r2= 0.9783).