Pain is an unpleasant sensory and emotional experience usually arising from actual or potential tissue damage. Acute pain can be a difficult medical problem to diagnose and treat. Pain sensitivity has proved to be extremely variable among human individuals and one of the most important factors for such variations in pain-related phenomena is genetic diversity. This book investigates the genetic basis of large individual differences in pain sensitivity. Also presented are ways to relieve pain including research results on the use of riboflavin and a B-vitamin, as an adjuvant in the treatment of pain and inflammation. Several articles focus on the pain in children and infants. Included is a look at psychometrically sound instruments to quantify children's acute pain and a review of the literature detailing how to inform and arm children and their parents for impending procedures.