We researched the spreading of Brucella ovis infection in sheep from the year 2002 to 2007 in Croatia. In 2002 and 2003. a total of 30 635 sheep blood samples were examined using the commercially available enzyme-linked immunosorbent assay (ELISA). In 2002, 1014 out of 14404 examined sheep blood samples (7%) from six counties gave positive reactions while 2060 (14.3%) were found suspicious. In 2003, 638 out of 16221 examined sheep blood samples in nine counties (3.9%) tested positive while 1083 (6.7%) were suspicious. In the year 2002 and 2003., serologic positive reactors were excluded from the breeding. Also, owners were recomended to keep separately young and old rams, and their testing before intake to breeding. Since the year 2004 serological testing of all breeding rams in the herd was carried out twice by complement fixation test. Positive reactions are additionaly testing by enzyme-linked immunosorbent assay. Positive rams are castrated and all herd is pronounced positive to Contagious Epididymitis in rams. It is also forbidden market and introduction of new animals in the flock. Separate holding and anew searching of negative rams is regulated in the period of 30 to 60 days. From the year 2004 to 2007 serological testing of all rams in the herd was carried out twice a year. In 2004 sera from 8323 rams were examined and positive results were observed in 212 rams (2.5%) in 14 localitys, in 2005 we examined 9526 bloods, and positive reaction was observed in 295 rams (3.1%) in 34 localitys, in the year 2006. sera of 11 856 rams were examined and positive results were observed in 267 rams (2.2%) in 20 localitys and finally in 2007 sera from 11013 rams of 20 localitys were examined and 216 (1.9%) animals were positive. During experimental period (2004-2007) all positive reactions to B. ovis infection by complement fixation test were confirmed by enzyme-linked immunosorbent assay. In comparison to period of 2002-2003, in the interval from 2004 to 2007, total number of positive rams decreased and some smaller closed breedings became free of disease, but complete eradication of ilness in some area is not accomplished. From 2002-2003, while serological diagnostic methods based on enzyme-linked immunosorbent assay only, larger number of positive and suspicious reactions were determined, whereas in the period of 2004-2007 we found fewer positive reactions to B. ovis infection. Besides well known immunological characteristics of B. ovis and limits of serological diagnostic methods, extensive farming and readiness (ability) of farmers to apply assigned measures of eradication, also contributing efficacy of suppressing illness.