The nociceptive flexion reflex and the crossed extension reflex are produced by the spinal cord to protect a limb from a source of nociception and potential tissue damage. Thus, nociceptive inputs activate flexor muscles and inhibit extensor muscles of the affected limb while producing the opposite effect on the contralateral flexor and extensor muscles. This constitutes the general rule observable for the reflex movements evoked from the limbs by stimulation of their peripheral afferents. As described by Brown and Sherrington in 1912, there are some exceptions to this rule, observable in the decerebrate or spinal cat, where ipsilateral extension or contralateral flexion can be elicited. However, no evidence of these exceptions has been described in man. In this study, the nociceptive flexion reflex was produced by stimulation of the right sural nerve using transcutaneous electrical stimulation. The stimulus intensity was adjusted individually at 120 % of the reflex threshold. To examine the spinal integration of bilateral inputs, a concurrent stimulus was delivered to the left sural nerve at different intensities and the amplitude of the right sural reflex was compared between four conditions: right ipsilateral stimulation adjusted individually at 120 % of reflex threshold (1); bilateral stimulation adjusted individually at 120 % of reflex threshold on the right and adjusted individually at 60 % (2), 120 % (3), or 140 % (4) of reflex threshold on the left. Results indicate that the right sural reflex was facilitated by contralateral stimulation. However, this occurred only for nociceptive inputs, for stimulation at 120 % and 140 % of reflex threshold on the left (p<0.001), and not for non nociceptive inputs, for stimulation at 60 % of reflex threshold on the left (p>0.1). This indicates that sural afferent stimulation can facilitate contralateral flexion. This is an exception to the rule of contralateral extension and represents an adaptive response for situations in which both limbs should be withdrawn from a source of nociception.