We describe a 68-year-old woman who had suffered pain, swelling, heat, and redness in the region of both clavicles for the last 2 years. Her erythrocyte sedimentation rate was markedly elevated; tests for rheumatoid factor were negative. At surgical exploration, ankylosis of the sternoclavicular joints, especially on the left side, was found. Biopsy revealed chronic nonspecific inflammation with new bone formation, consistent with the diagnosis of sternocostoclavicular hyperostosis or pustulotic arthroosteitis.