CHARACTERISTICS of muscular contraction induced by magnetic stimulation were studied using isolated gastrocnemius muscles of a frog. The figure-eight coil position was regarded as 0° when the direction of induced current was parallel to the muscle fiber axis, and 90° when the induced current was perpendicular to the muscle fiber axis. Muscular contraction readily occurred with lower outputs of magnetic stimulation at 0° and 180°, but it was weak at 90° and 270°. Magnetic stimulation did not directly induce muscular contraction but it acted on the synapses forming end plates to muscle cells, and muscular contraction occurred if the direction of the eddy current was parallel to the nerve which innervated the muscle cells.