Abstract We report the first outbreak of Acinetobacter species meningitis in a group of children with acute leukaemia following the administration of intrathecal chemotherapy. Eight of twenty patients receiving methotrexate injections on a single day developed signs and symptoms of meningitis within 18 h of treatment, and cases were clustered by time of administration. A cohort study comparing case and non-case patients did not identify any specific host factor associated with meningitis. Acinetobacter calcoaceticus var anitratus was isolated from the cerebrospinal fluid (CSF) of five patients; three patients died. Our investigation determined that the methotrexate was extrinsically contaminated by reused needles, used for reconstitution and administration, which had been inadequately sterilized. Acinetobacter calcoaceticus var anitratus was isolated from an autoclaved needle and a vial of methotrexate used for chemotherapy; these and the clinical isolates had similar antibiograms. After introduction of single-use disposable needles no subsequent cases occurred.