Mseleni Joint Disease (MJD), a polyarticular osteoarthritis of uncertain etiology is endemic among the Tonga-Zulu tribe. The traditional diet is deficient in calcium, and palm wine (2-4% alcohol) is drunk widely. Patients with MJD are reported to be more osteopenic than those without. Iliac bone biopsies of 19 arthritic patients were examined by routine histomorphometry and revealed decreased trabecular bone volume (p less than 0.0005), increased resorption surfaces (p less than 0.01), decreased bone formation rate at the BMU (p less than 0.01) level and increased mineralization lag time (p less than 0.01). Six of the 19 patients (31.6%) had features of osteomalacia and six (31.6%) signs of osteoblast failure. The most likely cause of the bone disorder is calcium deficiency, but inanition, inactivity and alcohol abuse may have contributed. Although the joint disorder may have contributed to the bone disorder, the converse is unlikely the case.