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iscovery Women are at greater risk for experiencing many forms of func-tional pain disorders, including irritable bowel syndrome (IBS) [25,44]. The belief that sex differences in visceral nociception stem, at least in part, from differences in neural processing of the noci-ceptive input has initiated examination of sex differences in IBS pa-In a H215O positron emission tomography (15O-PET) study, Naliboff et al. [29] reported that in response to 45-mmHg rectal distension, female IBS patients show greater activation in limbic areas (including the ventromedial prefrontal, anterior and infrage-nual cingulate cortices, and amygdala), whereas males showed greater activation in the dorsolateral prefrontal and insular corti-ces, and dorsal pons. The pattern is consistent with greater cogni-tive processing in males, but greater emotional responses in females. In an earlier 15O-PET study, Berman et al. [1] also noted greater activation of the insula in male than in female IBS patients