We retrospectively reviewed all patients with a final diagnosis of spontaneous thoracic aortic dissection treated at Linkou Chang Gung Memorial Hospital between January 1989 and December 1994. There were a total of 109 patients with a mean age of 55 +/- 11 years ranging from 19 to 88 years. The male-to-female ratio was 2 to 1 (73 to 36). There was a predilection to present during the colder months, with 69% seen between September 1 and February 28 and only 31% during the warmer half of the year. In most patients, hypertension (85%) was the major predisposing factor with another 7% having Marfan syndrome. The remaining 8% had no obvious underlying disease except for one patient who had an atrial septum defect. Presenting chief complaints in order of frequency included: anterior chest pain 58.7% (64/109), back pain 19.2% (21/109), abdominal pain 10.1% (11/109), consciousness change 3.7% (4/109), neck pain 2.7% (3/109), paraparesis 2.7% (3/109), dyspnea 1.8% (2/109), and hemoptysis 0.9% (1/109). The diagnostic breakdown revealed 46% to be type A (50/109) and 54% type B (59/109). A total of 26 (24%) patients died in hospital (16% were type A and 8% were type B). (Type A included all proximal dissections and those distal dissections that extend retrograde to involve the arch and ascending aorta; Type B refers to the other distal dissections without proximal extension; proposed by Daily et al.) Thoracic aortic dissection remains an important concern in patients with a history of hypertension. Patients seem particularly susceptible during cold weather months. The average age of our patients was only 55 years and 24% of them died during hospitalization. Earlier identification and more aggressive antihypertensive treatment is required.