Repetitive transcranial magnetic stimulation (rTMS) has been suggested as antidepressive treatment strategy. The mechanism of action by which the antidepressive effect is brought about remains unclear at present. Here, we report findings in a patient suffering from recurrent major depression and rheumatoid arthritis. Improvement of depressive symptoms during 20 Hz rTMS of the left dorsolateral prefrontal cortex was repeatedly associated with a systemic inflammatory reaction, suggesting that rTMS induced an immunomodulatory effect.