Total fasting induces within a few days a substantial reduction of joint pain, swelling, morning stiffness, and other arthritic symptoms in patients with rheumatoid arthritis. This remission subsides slowly after discontinuation of fasting. Its mechanisms are complex and involves diminished activation of neutrophils and lymphocytes and decreased generation of leukotrienes and of concentrations of serum complement factors, as well as of other proinflammatory systems. Moreover, ketosis and other metabolic and endocrine changes may be of significance for symptom expression and recognition.