We investigated how the administration of different dosages of nabilone (Cesamet®), a synthetic analog of Ä9-tetrahydrocannabinol, may affect the experience of pain. By measuring subjective pain ratings caused by a continuous thermal stimulation kept at a fixed temperature level, it was possible to investigate how nabilone affects pain sensitization. Seven healthy volunteers participated in this project and were seen three times, corresponding to the double-blinded administration of placebo, 0.5mg and 1mg doses of nabilone. At the beginning of each experimental session, a continuous painful thermal stimulation on the forearm was given for a period of 2 minutes (time 1). Activation of an endogenous opioidergic inhibitory control of pain called diffuse noxious inhibitory control (DNIC), activated by immersing the subject's arm in cold water (7° C) for a period of 2 minutes, then followed. Another painful thermal stimulation was repeated afterward (time 2). At the end of this first experimental block, a dose of nabilone was taken by the subject. Following a 2 hour waiting period, measures taken at time 1 and 2 were repeated (time 3 and 4). A continuous painful thermal stimulation during 2 minutes creates spinal sensitization, making it possible to analyze this phenomenon. Differences between pre and post administration of nabilone as well as pre and post DNIC activity were then analyzed. Our datas did not show a significant reduction of pain between the 1mg dose of nabilone and placebo. Importantly, however, nabilone significantly increased DNIC induced analgesia (P_1-tailed<.05, R2=.397), limiting the temporal summation of pain. This suggests that cannabinoids may potentiate the analgesic properties of endogenous opioid systems present in humans.