IL-2 and IL-15 were tested for effects on responses to mechanical or thermal stimuli when spinally administered to male Sprague-Dawley rats with surgically implanted intrathecal catheters. Restricted doses of both IL-2 and IL-15 produced increased responsiveness to mechanical stimulation of the hindpaws. This effect lasted up to 48 h. IL-2 had biphasic effects on thermal responses whereas IL-15 produced thermal hypalgesia alone. These effects dissipated within 24h. These results suggest that IL-2 and IL-15 may participate in the generation of hyperalgesia in some pain conditions.