Acute tumour lysis syndrome (ATLS) is a common complication of the treatment of haematopoietic malignancies. It is also well recognized in many nonhaematopoeitic malignancies of adults. There are very few reports of the syndrome occurring during therapy for the nonhaematopoeitic malignancies of childhood, and none has previously been reported in the treatment of neuroblastoma. We report the cases of four patients presenting to The Hospital for Sick Children (HSC) between 1985 and 1992 who developed ATLS during treatment for stage IVS neuroblastoma. ATLS is a significant risk in patients undergoing therapy for stage IVS neuroblastoma, particularly where this has been delayed.