We describe an outbreak of Gram-negative septicaemia due to a rare, non-fermenting, aerobic organism, Acinetobacter calcoaceticus var. lwoffi. The outbreak occurred on a neonatal unit and was confined to babies who were receiving parenteral nutrition. Seven babies developed septicaemia within 24 hours. The source of the outbreak was never firmly established, but contamination of the parenteral nutrition fluid was considered most likely. All 7 babies recovered uneventfully after a week's course of intravenous ceftazidime. Thrombocytopenia was an unexpected feature of this infection.