A prospective study on the epidemiology of adverse drug reactions (ADR) in the 200 neonates consecutively admitted to a newborn intensive care unit had shown that 136 ADR occurred in 60 babies (incidence = 30%). 20 of these ADR (14.7%) were major (life-threatening), 34 (25%) were moderate (prolonged hospital stay) and 82 (60.3%) were minor (resolved spontaneously, no therapy required). Respiratory depression, cardiac arrhythmias, renal failure, metabolic abnormalities (hyperglycemia, electrolyte imbalance) and gastrointestinal bleeding were the most common major and moderate ADR. Hematologic (eosinophilia, thrombocytopenia) and metabolic (lipemia, hyperglycemia) were the most frequent minor ADR. The case fatality rate is 5%. Most commonly suspected drugs associated with the ADR were cardiovascular drugs (tolazoline, digoxin, methoxamine), antibiotics, diuretics and components of intravenous nutrition solutions.