We surveyed the 20-year outcome of a cohort of patients with Behçet syndrome with emphasis on both mortality and morbidity. During 1999 and 2000, we collected outcome information on 387/428 (90.4%) of a cohort of patients (262 male, 125 female) who had registered in a dedicated outpatient clinic between July 1977 and December 1983. In 245/345 (71.0%) patients, outcome information was based on a formal hospital reevaluation, and in the remaining patients, on detailed telephone interviews. Forty-two patients (9.8%) (39 male, 3 female) had died, mainly due to major vessel disease and neurologic involvement. Mortality, as measured by standardized mortality ratios (SMR), was specifically increased among young males, among whom morbidity was also the highest. However, the SMR tended to decrease significantly with the passage of time. The same was also true for all mucocutaneous and articular manifestations. Both the onset of eye disease and its greatest damage were also usually within the first few years of disease onset. These suggest that the "disease burden" of Behçet syndrome is usually confined to the early years of its course, and in many patients the syndrome "burns out." However, central nervous system involvement and major vessel disease are exceptions. They can have their onset late (5-10 yr) during the disease course. As reflected in the mortality figures, the disease was less severe among the females for almost each disease manifestation. There were no female patients with arterial aneurysms. Severely impaired vision did not always mean an eventual loss of useful vision, and those patients with a late onset of eye disease had a better visual prognosis.