目的：分析儿童不明原因晕厥的常见诱因。方法：详细询问2006年1月至2011年10月就诊的434例不明原因晕厥儿童（3.0～17.9岁，男192例，女242例）的晕厥病史及诱因，分析诱因在不同年龄、性别、晕厥频次、直立倾斜试验（HUTT）结果之间的差异。结果：（1）偶发晕厥常见诱因依次为持久站立（30%）、运动（13%）、体位改变（9%）、坐位（7%）、玩耍（6%）等。①性别比较：持久站立引起的偶发晕厥女性较男性多见(P<0.01）；排尿晕厥主要见于男性；闷热环境主要诱发女性晕厥。②年龄比较：体位改变诱发偶发晕厥在≥12岁组较<12岁组常见（P<0.05），其余诱因在不同年龄间差异未见统计学意义。③不同HUTT结果比较：体位改变诱发偶发晕厥多见于HUTT阴性组（P<0.05）。（2）所有偶发晕厥诱因均可诱发反复晕厥，56.2%的反复晕厥为同一诱因所致。结论：儿童不明原因晕厥常见诱因为持久站立、运动、体位改变等，临床上避免诱因有助于预防晕厥发作。

OBJECTIVE: To investigate the common causes of unexplained syncope in children. METHODS: A total of 434 children with unexplained syncope who were aged from 3.0 to 17.9 years (192 males and 242 females) and who saw the doctor between January 2006 and October 2011. were examined in order to explore the detailed histories and causes of syncope and to analyze variance in causes among different ages, genders, syncope frequencies and head-up tilt test (HUTT) results. RESULTS: (1) The causes of occasional syncope included persistent standing (30%), movement (13%), change in body position(9%), sitting(7%), and playing(6%). Persistent standing was more common as a cause in females than in males (P<0.01). Micturition syncope was mainly seen in males. Sultry weather was the main cause of syncope in females. Change in body position was a more common cause in the ≥12 years group than in the <12 years group (P<0.05), while other causes showed no significant differences among different age groups. Change in body position was a more common cause of syncope in children with negative HUTT results than in those with positive HUTT results (P<0.05). (2) All causes of occasional syncope can induce repeated syncope, and most repeated syncope (56%) had the same cause. CONCLUSIONS: The common causes of unexplained syncope include persistent standing, movement and changes of body position in children. Avoiding these causes is helpful for prevention of childhood syncope.