The prevalence of bovine brucellosis was measured in cross sectional study in Jimma zone, Western Ethiopia using RBT and CFT from October 2003 to April 2004. The study animals consisted of 1813 cattle among which were 1305 local breed found in extensive system in five districts and 508 cross breed in 46 farms found in Jimma town. The overall individual animal prevalence of 0.77 % and 0.2 % were recorded in five districts and Jimma town, respectively. When the two management systems were considered together an overall individual animal and herd prevalence of 0.61 % and 2.9 % were found, respectively. Higher prevalences were observed in larger herd size (P< 0.001); older age group were affected more than younger animals (P< 0.05) in the extensive management system. No reactors were observed in male. Seropositivities of 8 % were observed in animals with previous history of abortion. In the study of the disease in human beings, classified in four high-risk occupational groups, using RBT and CFT, the highest prevalence (14.3%) was observed among animal health workers and followed by farmers (3.2 %) and there was no reactors found among butchers and abattoir workers. An overall prevalence (2.4 %) was found in the area. There was a significantly higher risk of acquiring the infection when handling parturient animals (P< 0.05). The study demonstrates that the prevalence of brucellosis in the area is low; however, there is probable risk of spread of the disease in the unaffected cattle population since there are no precaution measures taken in the areas that should have been practiced by farmers. Since the prevalence is below 2 %, test and slaughter with compensation payment to farmers is recommendable, while in case of human brucellosis, since its presence is confirmed and the risk factors are identified, the medical personnel should give attention as to differential diagnosis of the disease which have been overlooked so far.