The authors treated 31 patients with septic arthritis of the sacroiliac joint (14 patients with tuberculosis, 7 acute staphylococcal, 6 gonococcal, and 4 typhoid). The clinical presentation was vague and nonspecific, but most patients reported buttock pain, low back pain and difficulty walking. In 28 patients, the diagnosis was established after clinical examination, bone scans, hematologic investigations, and blood cultures. The diagnosis was established through arthrocentesis of the sacroiliac joint in 9 patients. In 3 patients, there was a delay in diagnosis. Twenty-nine patients improved on a conservative regimen of bed rest and antibiotics. Two patients required open drainage because of a large buttock abscess that was secondary to tuberculosis sarcoiliitis.