Abstract: This invention relates to a method for treating a subject with irritable bowel syndrome (“IBS”) which comprises long-term administration of an opioid receptor antagonist at an appropriately low dose which will selectively antagonize excitatory opioid receptor functions, but not inhibitory opioid receptor functions, in myenteric neurons in the intestinal tract as well as in neurons of the central nervous system (“CNS”). The administration of the opioid receptor antagonist at a low dose enhances the potency of the inhibitory effects of endogenous opioid peptides present in the intestinal tract and the CNS, thereby reducing abdominal pain and stool frequency resulting from abnormally supersensitized excitatory opioid receptor functions. The invention also relates to a composition for treating a subject with IBS, which comprises an effective dose of an opioid receptor antagonist, and a pharmaceutically acceptable carrier.