Competitive ELISA methods were used to measure the level of aflatoxin M1 (AFM1) from urine in 1008 Korean adults. Subjects were selected by random sampling in all areas of Korea, except Cheju-do. The recovery rate of AFM1 using this method was 105% (73-124%). The geometric mean of urinary AFM1 in all subjects was 3.43 pg/mL (3.67 ng/g creatinine). The level of AFM1 in males was statistically higher, compared with female subjects. However, the levels of AFM1 did not differ according to age. Subjects in Chungbuk-do showed the highest urinary AFM1 concentration, whereas subjects in Kyeongnam-do showed the lowest concentration. Assuming an excretion rate of 5%, this AFM1 excretion corresponds to approximately 0.1 microgram/day in Korean adults.