Owing to their nutritional value, dairy products were popular in Taiwan. Aflatoxin M1(AFM1) was the metabolite of potential carcinogen aflatoxin B1 and found in dairy products. An analytical method using immunoaffinty column for extraction and HPLC for quantification was developed for AFM1. The detection limits for fresh milk (pasteurized milk), milk powder and drinking yogurt (0.002, 0.02 and 0.005 ppb, respectively) were 10 times lower than that in the former survey. The recoveries of AFM1 from fresh milk were 83.3 ± 2.9 and 89.5 ± 2.9% at 0.5 and 0.05 ppb spiked levels, respectively. Spiked 5 and 0.5 ppb AFM1 in milk powder, the recoveries were 86.0 ± 1.9 and 88.7 ± 1.9%, respectively. The recoveries of AFM1 from drinking yogurt were 99.9 ± 1.4 and 94.8 ± 3.2% at 0.5 and 0.05 ppb spiked levels, respectively. It was the first time AFM1 was tested in drinking yogurt in Taiwan in this survey, and the performance for detecting AFM1 in drinking yogurt was also evaluated through attending an international proficiency test. Our laboratory got a satisfactory result. In order to survey AFM1 contents in dairy products, 44 samples of fresh milk, 45 samples of milk powder and 24 samples of drinking yogurt were collected from supermarkets, convenience stores and drug stores located in 23 counties of Taiwan from June to August, 2002. The results showed that AFM1 was detected in 40 samples of fresh milk at 0.002~0.083 ppb level. AFM1 was not found in all milk powders. AFM1 was detected in 3 samples of drinking yogurt, at the level of 0.007, 0.009 and 0.044 ppb. According to the food sanitary standard regulation in Taiwan, the action levels of AFM1 were 0.5 ppb, 5 ppb and notdetectable for fresh milk, milk powder and infant formula products, respectively. The 113 samples collected in this survey all met the regulation requirements.