In an 11-year retrospective study of coroner's autopsies on the Hawaiian island of Kauai, it was found that an unusual and apparently unique subset of travelers died suddenly. Death was caused by coronary arteriosclerosis, was characterized by acute coronary changes, and occurred in a group younger than the usual age for sudden cardiac death. Visitors with two-vessel disease had an incidence of sudden death nearly four times that of Kauaians (p < 0.02), with a ninefold increase of coronary thrombosis (p <0.001), a sixfold prevalence of old myocardial infarcts (p < 0.001). The circadian pattern of these deaths was different from that previously described in acute myocardial infarction or sudden death, with the number of incidents rising steadily through the day in contrast to the morning peak described in previously published series. The syndrome was expressed in decedents with two-vessel coronary disease either with acute coronary artery lesions-thrombosis, hemorrhage in a plaque, or ruptured coronary artery-or no lesions, presumably spasm. Underlying chronic processes included enlarged heart or old myocardial infarct, which both occurred with a significantly greater incidence in travelers than in local residents, and in a totally different pattern from that occurring in subjects with three-vessel disease. It is postulated that the syndrome is caused by stress related to travel and time zone changes.