BACKGROUND: Intrathecal administration of vincristine is a rare event but catastrophic for the patient, family and clinical team involved. Analysis of this source of harm shows it to be a classic systems error which has proved intractable for nearly 40 years. Failure to learn from history, communicate safety solutions nationally and internationally, create safety agencies which effectively and reliably prevent adverse events, conduct investigations and enquiries which fully reveals how to mitigate system error, develop robust physical design solutions to prevent harm to patients, make effective solutions universal and preparing for the unexpected are all major challenges. CONCLUSIONS: The elimination of rare yet catastrophic errors like this remains one of the tests of whether we can make healthcare safer. In this paper, we discuss why effective learning has been so slow and illustrate lessons for other fields of patient safety.