In 8 patients affected with rheumatoid arthritis the effects of levamisole administration (150 mg/day once a week) on plasma immunoglobulins were studied. The concentration of IgG, IgA and IgM was measured before and after 15,30,60 and 90 days of treatment. We observed a significant increase of IgG after 30, 60 and 90 days, of IgA after 30 and 90 days, and of IgM after 15 and 30 dyas. Such response is in contrast with previously reported decreased of immunoglobulins most frequently observed after 6 months of drug administration. Therefore, it seems that levamisole at the beginning of its activity on immunocompetent cells enhances rather than decreases the antibody production.