This study was conducted on 210 sheep in Maku area in Iran in order to determine seroprevalence of leptospiral infection. Sera were initially screened at dilution of 1: 100 against 8 live serovars of Leptospira interrogans: Pomona, Canicola, Hardjo, Ballom, Icterohaemorrhagiae, Automenalis, Australis and Grippotyphosa using the microscopic agglutination test. The prevalence of leptospiral infection (At titers 100 and 200) was 15.23% in sheep. There was a significant relationship between aging and the incidence of leptospiral infection (P<0.05); however no significant relationship between breed of the shepp and the incidence of leptospiral infection was found. The highest number of reactors in sheep (62%) was due to serovar Canicola, followed in descending order by Icterohaemorrhagiae (32%) and Hardjo (6%). All of the sera were seronegatives for Pomona, Ballum, Grippotyphosa and Autominalise. The majority of titre levels were between 100 and 200 for all the serovars. These results confirm that the majority of leptospiral infections is asymptomatic and the presence of antibodies in the absence of infection indicates exposure to the organism in these animals.