Behçet syndrome (also known as Behçet disease) is a rare condition that is associated with considerable morbidity. Cases of Behçet syndrome have been reported worldwide, but the highest prevalence occurs in countries that border the ancient Silk Route, such as Turkey and Iran. Although oral ulceration, genital ulceration and eye disease are the classic triad of manifestations, the cardiovascular, gastrointestinal, musculoskeletal and central nervous systems can also be affected. The syndrome is chronic and relapsing with some patients having benign episodes whereas others have more serious complications, including blindness or the rupture of a pulmonary arterial aneurysm. Diagnosing Behçet syndrome, particularly outside of endemic regions, often incurs a considerable delay owing to the rarity of this condition. Furthermore, a paucity exists of data from randomized controlled trials on the optimal therapeutic approaches to use in patients, as well as a lack of informative laboratory surrogate markers to monitor disease progression. This Review discusses the issues surrounding the diagnosis and differential diagnosis of Behçet syndrome and presents the current approaches to managing patients with this complex group of disorders.