The antinociceptive effect of alendronate was studied. The bisphosphonate was i.p. administered and two tests were carried out: acetic acid in mice and formalin test in rats. In the acetic acid test, alendronate induced a dose-dependent antinociceptive effect that was statistically significant for the doses of 10, 20 and 40 mg/kg, and could be detected 48 hr after its administration. In the formalin test, however, alendronate, at the doses of 10 and 20 mg/kg, did not modify the pain score nor the number of flinches, when it was administered either 30 or 60 min before the test. However it must be noted that doses inducing analgesic effect are close to those inducing toxicity.