Diagnosis of cause of syncope is very difficult and often unrewarding even though it is fairly common problem. Universally accepted guidelines are not well established till now and only expert consensuses are available for managing syncope patients. In this study we choose a subset of young adults presentating with syncope and did extensive clinical evaluation followed by routine 12 lead ECG and then subjected them to either Tilt Table Testing or Holter monitoring, and we could arrive to diagnosis of syncope in majority of our patients without doing extensive investigations. This book focuses on various theories/mechanisms of syncope and detailed explanation for them have been elucidated clearly. To improve the diagnostic yield of HUTT (Head Up Tilt Table) we analysed clinical predictors or likelihood ratios of positive tilt table test based upon routine clinical examination and also did Time Domain and Frequency Domain analysis of Heart Rate Variability during HUTT testing.