Although back pain is very common, the differential diagnosis may sometimes be very difficult. Both inflammation and infections of spinal or sacroiliac joints are examples of such causes. We report three cases of brucella sacroiliitis resembling acute low back pain or lumbar disc herniation. All patients had had a recent infection and were referred complaining of acute back pain with a suspicion of lumbar disc herniation. The complaints of all patients reduced dramatically after proper medication. Radiographs of all patients and bone scans of two patients revealed sacroiliitis. One of the patients was positive for HLA-B27; in the other two patients HLA-B27 could not be determined.