This paper reports on a sporadic, naturally acquired infection of sheep with Brucella abortus on a privately owned farm in Toro near Bauchi, Nigeria. The abortions, which occurred in a flock of 28 Yankassa sheep, involved five ewes at the third month of gestation. Serum and milk samples from the flock were examined for Brucella antibodies by the Rose Bengal plate test, serum agglutination test (SAT) and milk ring test (MRT). The proportion shown as positive by SAT was 14.3%. All the five milk samples examined by MRT were positive. A total of seven isolates of Brucella were obtained from three milk samples and four vaginal swabs collected from aborting ewes. All isolates were identified and biotyped as B. abortus biovar 1. This biovar was also isolated from cattle maintained on the farm in association with the sheep. The infection was attributed to the animal husbandry practices employed on the farm.