Objective To study the clinical value and safety of the head-up tilt table test(HUTT) in children under 6 years old.Methods The HUTT results between September 2000 and August 2011 of 144 2 to 6-year-old children(81 boys and 63 girls) with syncope and dizziness of unknown causes were retrospectively studied.Results Eight children completed the based tilt table test and 136 cases completed the sublingual nitroglycerin tilt table test.No serious side effects were found in these children.Thirty-two(22.2%) of th...