Two patients are described in whom arthritis following intestinal bypass surgery for obesity was associated with the presence of circulating immune complexes (CLC) and HLA B27. The arthritis was characteristically intermittent and controlled by low dose prednisone, indomethacin, and tetracycline therapy. The findings suggest that immune complexes play a role in the pathogenesis of arthritis associated with condition, and that perhaps the association with HLA B27 may predispose to the development of this complication.