Approximately 697000 United States military personnel participated in the Persian Gulf War (PGW) between August 1990 and March 1991. By April 1997, over 25% of veterans reported chronic health complaints of underdetermined etiology. Gastrointestinal symptoms were among the most frequently reported symptoms including abdominal pain and diarrhea. The objectives of this study were (1). to determine if PGW veterans chronic abdominal pain and diarrhea exhibit visceral and cutaneous hypersensitivity, (2). to determine if these differences in pain sensitivity are significantly associated with psychological stress. A total of 12 veterans (ten males, two females) (39+/-9 years) who were deployed to the Persian Gulf were enrolled. Seven civilians without prior military experience (five males, two females) and five veterans (five males) who had previously been deployed for active combat were enrolled as controls (35+/-9 years). All 12 PGW veterans reported chronic abdominal pain and diarrhea (negative diagnostic workup) that developed during their tour of duty in the Persian Gulf region. All patients completed a battery of psychological assessments and then randomly received experimental visceral (rectal distension of 35 and 55 mmHg for 30s) and cutaneous (immersion of right foot in 45 and 47 degrees C water for 30s) pain stimuli after which they rated their pain intensity and pain unpleasantness on a continuous visual analogue scale (M-VAS) scale. The trials were repeated and the mean M-VAS scores for the two trials were recorded for each subject. In comparison to controls, PGW subjects reported statistically significant higher mean ratings of pain intensity and pain unpleasantness in response to 35 and 55 mmHg rectal distention (P<0.001) and in response to 45 and 47 degrees C water immersion (P<0.001) of the hand and foot. Results of the hierarchical regressions indicated that the psychological measures (i.e. anxiety, somatic focus) accounted for a significant amount of variance in each of the pain measures. PGW veterans who developed chronic abdominal pain and diarrhea during their tour of duty exhibit visceral hypersensitivity similar to patients with the irritable bowel syndrome. These veterans also have cutaneous hypersensitivity and higher levels of anxiety and somatic focus accounting for these differences in pain reporting.