We describe two patients with clinical, radiological and laboratory findings consistent with transient regional osteoporosis. In both cases antinuclear and antiphospholipid antibodies were found with no evidence of any other autoimmune disease. Both patients were smokers. We suggest transient ischemia caused by antiphospholipid antibodies as a possible etiological factor in this rare and poorly understood syndrome, and hypothesize that anticoagulants and abstinence from smoking may play a role in the prevention of recurrence in these patients.