Aspergillus , Penicillium and Fusarium species are the most frequent toxigenic fungi found in Europe which produce aflatoxin B1 transformed into M1 in milk. This toxin is highly dangerous for human health, being carcinogens, mutagens and also teratogens. The aim of this study was to evaluate the incidence of M1 aflatoxin in cattle growth units for milk production and also in collecting units found in two surveillance systems from Transylvania. This incidence was further compared among these systems so as to establish the prevalence area of aflatoxin M1 occurrence in milk. The material used was represented by 141 raw milk samples analyzed and tested in 2 regional sanitary veterinary control laboratories by immuno-enzymatic ELISA method. Of the total samples, 56 were obtained from milk collecting units and 85 from growth units. The study shows that in 35.65% of the samples analyzed the identification of aflatoxin M1 was possible. Surprisingly, in the growth units with less than 100 individuals, aflatoxin M1 was identified in a proportion of 81.4%. None of the samples with M1 toxin exceeded the limit of 0.05 µg/kg, which is the maximum allowed. In the samples gathered from collecting centers from both surveillance systems a percent of 48 were identified with M1 afllatoxin, and 2 samples showed values that exceeded the one stated by the current legislation. When comparing the two surveillance systems we found significant differences (p<0.05), one being with a much higher prevalence and with positive samples. In one of the supervised areas there is a potential contamination hazard with AFM1, while in the second one the probability of contamination through milk consumption is very low. As consequence we further recommend that in the problem surveillance system a careful monitoring of feedstuffs to be made in order to prevent its occurrence in milk.