Many complications that followed jejunoileal bypass operations performed for the relief of morbid obesity were caused by bacterial overgrowth in the excluded blind loop. The arthritis-dermatitis syndrome was one of the common distressing disorders. The pathogenetic mechanism was thought to be an immune-complex-mediated process related to bypass enteritis. Antiarthritic medication was ineffective in most instances, and the skin lesions were refractory to treatment. A 45-year-old woman was suffering from the disorder as described above. She also had diarrhea, a low hematocrit, an elevated white blood cell count, and an increased sedimentation rate. Her nutritional status was satisfactory, presumably because of adaptive hypertrophy of the short functioning small intestinal segment. The patient adamantly refused dismantling of the bypass or any gastric restriction operations. Therefore, the blind loop, the source of her disease, was excised with immediate relief of all ill effects and restoration of normal laboratory findings. The patient has been entirely well since, and her weight has remained stable for one year.