Alendronate is a potent inhibitor of osteoclast-mediated bone resorption, but its use results in serious esophageal damage. In order to clarify the latter, we examined the effects of alendronate on electrical field stimulation-induced responses in the rat lower esophageal sphincter. Electrical field stimulation induced atropine-sensitive contraction. Alendronate inhibited electrical field stimulation-induced contraction in a concentration-dependent manner. In the presence of NG-nitro-l-arginine (l-nitroarginine), electrical field stimulation elicited a strong cholinergic contraction. This contraction was also inhibited by alendronate, to a similar extent as that seen in the absence of l-nitroarginine. In lower esophageal sphincter contracted by prostaglandin F2α and treated with atropine, electrical field stimulation induced l-nitroarginine-sensitive relaxation. Alendronate did not affect relaxation. These results suggest that alendronate decreases the tone of lower esophageal sphincter by inhibiting cholinergic nervous activity.