To investigate the phenomenon of acute psychiatric decompensation in travelers, charts of all psychiatric-emergency patients with a history of recent travel involving time-zone changes were reviewed at a major medical center in Honolulu, HI. Charts of a control group with no history of travel were also reviewed. Significantly more travelers than controls showed symptoms of depression and mania (P < .012). East-bound travelers were significantly more likely to show symptoms of mania than controls (P < .001). In an eastbound-versus-westbound comparison, significantly more eastbound travelers showed symptoms of mania, whereas significantly more westbound travelers showed symptoms of depression (P < .05). These findings support the phase-advance hypothesis of depression. Psychosocial and biologic factors that may contribute to psychiatric decompensation in travelers are discussed.