A survey was carried out on the 1639 serum samples of sheep in four different geographical regions of Iran; Caspian Sea, Mountainous area, Persian Gulf, Central desert. A strain of B.ovis was isolated from west Azarbayjan inoculated to splenectomised lamb and the Blood obtained from the lamb contained about 10% infected erythrocytes used as antigen. Blood-antigen smears of B.ovis used to detect positive sera by indirect fluorescent antibody test, overal, 36% of samples were found to be positive for B.ovis. the antibody was detected in two age grouping of under and over two years age old, the infection rate was 35.9% and 38.87% respectively, the result indicated that 38.98% of ewes and 37.96% of rains were serum positive, the occurrance of infection in regions 1,2,3 and 4 were 15.93%, 58.81%, 12.04%, 13.22% respectively, these results sugqest that infection with B.ovis is wide spread throught Iran and prevalance of B.ovis in mountainous area was significantly higher than other regions (P<0/0005).