Aflatoxin M1 (AFM1) appears in milk as a direct result of the ingestion of food contaminated with aflatoxin B1 by cattle. The role of milk in human nutrition is well-known. The aim of this study was to evaluate Aflatoxin M1 contamination in pasteurized milk samples in Tabriz city (Iran) by ELISA (Enzyme Linked Immunosorbent Assay). Fifty pasteurized milk samples from different supermarkets in Tabriz city were collected during 6 months (July to December 2008). AFM1 was found in 100% of the examined milk samples. Sixty-two percent of the samples had AFM1 greater than the maximum tolerance limit (50 ng/l) accepted by European Union. It can be concluded that AFM1 levels in the samples purchased in Tabriz city, appear to be a serious public health problem at the moment. To achieve a low level of AFM1 in milk, dairy cows' feed samples from various cows' herds must be controlled periodically for aflatoxin and kept away from fungal contamination as much as possible.