Competitive ELISA methods was used to measure the level of aflatoxin M1 (AFM1) from urine in 1008 of Korean adults. Subjects were selected by random sampling in all area of Korea except Cheju-do. The recovery rate of AFM1 in 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 male showed statistically higher than one in female subjects. However, the levels of AFM1 were not different according to their age. The subjects in Chungbuk-do showed the highest urinary AFM1 concentration, whereas the subjects in Kyeongnam-do showed the lowest one. Assuming an excretion rate of 5%, this AFM1 excretion corresponds to about a 0.1 microgram/day in Korean adults.