Genomic configuration and expression of the N-myc gene was investigated by Southern and Northern blot analyses in 18 neuroblastomas of different clinical stages. We observed a 4-100-fold amplification of this oncogene in one of six stage III, two of four stage IV as well as one of five stage IVS tumours. Remarkably, an 80-fold N-myc amplification was demonstrated in a patient with stage IV neuroblastoma being in remission for more than 2 years; moreover, a 100-fold amplification could be detected in a stage IVS tumour from a newborn. These data are discussed in view of the recently postulated close association of N-myc amplification with rapid progression of neuroblastomas.