The neurophysiologic mechanisms involved in nonorganic paralysis are unclear. Because there is no established standard therapy, the authors investigated the effect of repetitive transcranial magnetic stimulation (rTMS) in four patients with nonorganic limb paralysis. Within the framework of a treatment trial, the patients were treated over a period of 5-12 weeks with rTMS applied to the contralateral motor cortex. Stimulation frequency was 15 Hz, train length 2 seconds, intertrain interval 4 seconds; daily total number of stimuli 4000. In one patient, motor function was completely restored; two patients experienced a marked improvement correlating with rTMS treatment. By contrast, one patient who had been diagnosed as a malingerer did not improve. Apart from possible favorable psychological factors that could partly explain the rTMS-associated effects, high-frequency rTMS might have enhanced or substituted an insufficient input to the motor cortex from failing frontal executive areas, and thereby opened the way to a learning process that lead to the reacquisition of limb use. rTMS may have a therapeutic effect in motor conversion disorder and may help elucidate neurophysiologic aspects of this condition. The potential benefit of rTMS in motor conversion disorder should be evaluated in larger, controlled samples.