The analgesic efficacy of dexmedetomidine (DEX)--a novel alpha 2-adrenoceptor agonist--was studied in man. Single intravenous doses of fentanyl (FEN; 2 micrograms/kg), DEX (0.25, 0.50 and 1.0 micrograms/kg) and placebo were administered to 5 healthy male volunteers in a double-blind, crossover study in randomized order. The analgesic effect of the different treatments was measured by determining the time course of pain threshold with dental dolorimetry and by quantitating subjective pain induced by a standard ischemic pain stimulus on the upper arm using a visual analogue scale (VAS). The drugs were generally well tolerated. FEN and DEX both had analgesic effects on ischemic pain, which was seen as a statistically significant decrease in subjective VAS ratings. FEN appeared to be more effective than DEX; the difference was not, however, statistically significant. Neither of the drugs affected the pain threshold measurements.