In the twenty years since the first case of neonatal drug addiction (resulting from the mother's use during pregnancy of morphine, heroin, methadone, cocaine) was referred to our attention, there has been a steady increase in the number of cases per year. Heroin alone or in association with methadone now represents the drug used by approximately 80% of addicted mothers. Over the past few years the mean age of mothers has increased; the number of drug users who do not appear to be addicts has also increased and a number of cases have lately been discovered only on the basis of neonatal symptoms, without any previous anamnestic indication. Neonatal abstinence syndrome (NAS) is the most striking effect of fetal exposure to drugs. Symptoms are easily recognised; pharmacological treatment can consist of either sedatives or replacement drugs whose dosage depends on the severity of withdrawal symptoms evaluated using a score system. NAS symptoms are usually resolved within a few days although some signs, especially irritability and tremors, may persist until 3 months of age. The main concern at present regards the future of these neonates. The most severe risk to which they are exposed, after HIV infection, is social; during the past few years in over 50% of cases parental authority has been suspended by the juvenile court. No long-term neurologic or cognitive deficits are directly associated with heroin or methadone use during pregnancy.