Effects of a potent neurotropic mycotoxin, fumitremorgin A (FTA), on the spinal cord were studied, using rabbits lightly anesthetized with urethane and chloralose. Spontaneous discharges of L₇ spinal ventral roots and common peroneal nerves were increased after intravenous injection of 100-200 μg/kg of FTA. Their abnormal discharge pattern represented the convulsive effect of FTA. Spinal monosynaptic reflexes became irregular in amplitude, with a slight predominance of smaller reflexes. Polysynaptic reflexes were inhibited in many cases. These FTA-induced changes in ventral root discharges and spinal reflexes were abolished by spinal transection at a segment of the upper level. These results suggest that FTA may have no direct facilitatory action on spinal motoneurons and that its remarkable motor effect has its origin in the supraspinal central nervous system.