The purpose of this paper is to study prognostic factors in neuroblastoma patients treated with high-dose chemotherapy and hematopoietic stem cell transplantation. Two hundred and eighteen children over 1 year of age and treated for stage 4 neuroblastoma were enrolled in this study. The median age at diagnosis was 39 months, the sex ratio 1.5 and 84% of patients had an abdominal primary tumor. Skeletal disease was detected in 79% of cases and bone marrow involvement in 93%. N-myc oncogene amplification was present in 27% of the patients studied. The probability of event-free survival at 5 years post-diagnosis was 29% in this series. Three major favorable prognostic factors were significant and independent in the multivariate analysis: age under 2 years at diagnosis (P<0.01), absence of bone marrow metastases at diagnosis (P<0.04) and the high-dose conditioning regimen containing busulfanmelphalan combination (P = 0.001). The quality of response to conventional primary chemotherapy was close to significance (P = 0.053). We conclude that factors related to the patient (age) and extent of disease are predictive of outcome in patients with neuroblastoma treated with conventional chemotherapy followed by surgical excision of the primary and consolidation with high-dose chemotherapy. They should be taken into account in future prospective studies. Moreover, the type of conditioning regimen appears to be the most important prognostic factor. This should encourage new investigations into innovative drug combinations.