Using nucleic acid analysis and in situ hybridization we have demonstrated N-myc amplification and expression in two children with a localized (stages I and II) stroma-rich neuroblastoma (NB) (ganglioneuroblastoma). The phenomenon was observed in both undifferentiated and mature ganglion-like cells. The two children are alive and disease-free without any treatment after 16 and 17 months. These observations suggest that morphologic differentiation in NB in vivo is not necessarily followed by a decrease in N-myc expression. Moreover, N-myc amplification does not represent an adverse prognostic factor. In contrast with what happens in undifferentiated NB, N-myc amplification does not have an adverse effect on prognosis when occurring in localized (stages I and II), stroma-rich NB with a favorable histology.