Since there is little information regarding the possible prognostic significance of tumor rupture in localized neuroblastoma, we have analyzed the clinical courses of 163 children registered from 1979-1990 in 12 italian pediatric oncology Centers participating in the Neuroblastoma Cooperative Group of the A.I.E.O.P. (Italian Association for Paediatric Haematology-Oncology). Ten instances (6%) of tumor rupture were described. Ruptures occurred preoperatively in one child, during the operation in 9; among these 9, two were provoked by the surgeon to allow radical tumor excision, 7 were accidental. Of these 10 children, 7 relapsed at 3-25 months (median, 8 months) from diagnosis. Relapses were local in 5 children (2 of the 5 died), disseminated in one (who died), local + disseminated in one (presently alive with disease). Two local relapses were followed by bony or haematologic spread at 4 and 8 months, respectively. Of the 7 children who relapsed, 2 are alive in complete remission at 29, 100 months, respectively; two are alive with disease at 3 and 65 months, 3 died at 8, 15 and 24 months, respectively. We conclude that rupture of a localized neuroblastoma is a factor predisposing to relapse and may compromise the chance of cure. The surgeon should be aware of the risks connected with this complication and make any effort to avoid it.