New finding: transient horizontal pendular nystagmus as a sequella to post-natal withdrawal syndrome. BACKGROUND: Children born of mothers who abused illegal substances during pregnancy can present with signs and symptoms of a withdrawal syndrome, including irritability, jitteriness, diarrhoea. Usually these symptoms appear from a few hours up to a few days after birth. It is frequently followed by a post-withdrawal period of several weeks duration with crying, excitability, sleep irregularities and feeding difficulties. The purpose is to report the presence of nystagmus in infants born from drug-addicted mothers. METHODS: Five children born from drug-addicted mothers were examined. RESULTS: Three children (case 1 - 3) presented with congenital horizontal pendular nystagmus. Two other children (case 4 - 5) presented with a peculiar transient horizontal nystagmus, lasting 6 months and 7 months respectively. CONCLUSIONS: To our knowledge, transient horizontal pendular nystagmus has never been reported in the literature. It was detected in two children who suffered from a post-natal withdrawal syndrome necessitating substitution therapy, including morphine. This may represent a form of morphine midbrain toxicity.