Effects of human calcitonin (HCT) on the responses of mice and rats to noxious stimuli of various types and morphine-antinociception in the mice tail-pinch method were studied as compared with procine calcitonin (PCT). I.c.v. administration of HCT (0.007-0.071 mg/mouse) delayed response time to tail-pinch stimuli and suppressed acetic acid writhing dose-relatedly. PCT (0.5-3 U/mouse, i.c.v.) exerted a dose-related antinociceptive effect in the tail-pinch and acetic acid writhing methods. The antinociceptive effect was also produced by s.c. administration of HCT (0.071-7.1 mg/kg) and PCT (10-1000 U/kg) in the tail-pinch and writhing methods, while the antinociceptive effect was not detected by the tail-flick method following i.c.v. and s.c. administration of HCT and PCT. Increase in response threshold in the hind paw pressure test was produced by 0.071-7.1 mg/kg, s.c. of HCT and 10-1000 U/kg, s.c. of PCT in rats. Inhibition of writhing due to i.c.v. administration of HCT and PCT was not antagonized by naloxone. Pre-drug control response time to tail-pinch stimuli tended to be shortened after 7-14 days of s.c. treatment with CT, especially with PCT. Pretreatment with HCT and PCT exerted no obvious influence on their acute effects. Morphine-antinociception in the tail-pinch method tended to be potentiated by single s.c. dose of HCT and to be decreased by 14 days chronic s.c. treatment with HCT. The role of calcium in HCT action was discussed.