Aflatoxin M1 (AFM1) is a hydroxylated metabolite of the carcinogen aflatoxin B1 (AFB1), and may be found in the milk of lactating animals that have ingested feedstuffs contaminated with AFB1 Between Jun 2010 and March 2011, 149 samples of pasteurized (n=90) and UHT (n=59) milk were collected from supermarkets in the cities of Shiraz, Khuzestan and Yazed, Iran. All samples were analyzed for AFM1 contamination by ELISA and 142 (95.3%) were positive with mean concentrations 41 ng.l^-1. These concentrations are lower than the standads of Codex Alimentarius and FDA (500 ng.l^-1), but 33 samples (22.1%) had higher concentrations than the maximum tolerance accepted by some European countries (50 ng.l^-1). Mean concentrations of AFM1 in pasteurized and UHT milk were 39 and 46 ng.l^-1, respectively. Mean concentrations of AFM1 in fall and winter samples were significantly higher (P<0.05) than those of summer but differences between AFM1 concentrations of fall and winter samples were not significantly different. No significant differences in Concentrations of AFM1 in milk samples between Shiraz, Khuzestan and Yazd. Considering the results, this survey revealed a high frequency of AFM1 contamination in milk samples from central part of Iran.