Jaundice in the newborn is usually normal. It is caused by the breakdown of red blood cells, which, as a result of newborn transitional physiology, results in the build-up of bilirubin in the infant's circulation. Bilirubin can be toxic, however, particularly in the brain, where its presence can result in death, or devastating long-term neurological damage. This article reviews factors that might result in the excessive production or build-up of bilirubin, as well as those that might predispose an infant to neurotoxicity.