EPSPs evoked by air puff stimulation of the hairy skin of the hindlimb or by low strength stimulation of the lateral sural nerve were facilitated by radiant heat of 50-53 degrees C but not by radiant heat of 42-43 degrees C. The results indicate that afferents from low threshold mechanoreceptors and from nociceptors of the skin converge onto common interneurons in reflex pathways to alpha-motoneurons. This would allow a functionally useful cooperation of these two types of afferents in spinal motor control.