The present experiment was designed to locate spinal neurons which are activated by afferent fibers in the ventral roots, and once found, to study their receptive field and rostral projection. After dorsal roots L1 approximately S4 on the left side were cut under a binocular microscope, stimulus was applied to ventral roots and extracellular responses were recorded using a glass microelectrode filled with fast green FCF. Sixty-four neurons were activated by stimulating ventral roots at 1.2-27.8 x T of the lowest threshold fibers of the ventral root. Six neurons were classified as wide dynamic neurons and 29 as high threshold neurons according to their response patterns to the periphery. Twelve neurons out of 29 were unresponsive to cutaneous stimulation, and located lamina V, suggesting that they innervate visceral organs. Thirty-five neurons (54.6%) were nociceptive nerons, most of which were located in laminae V and VI. In 6 neurons out of 35 nociceptive neurons (17.1%), rostral projection was confirmed by the collision block method and the ability to respond to high frequency stimuli with constant latency. Our results suggest that some spinal neurons activated primary affernt fibers in ventral roots stimulation are nociceptive and some of them are rostral projecting neurons which are antidromically activated ventral quadrants of the spinal cord.