Chromosomal band 1p36 probably harbours several neuroblastoma suppressor genes. A neuroblastoma patient has been described with a constitutional balanced translocation, t(1;17)(p36;q12-21). Cytogenetically, no loss of chromosomal material was visible. The 1p36 translocation breakpoint could therefore have inactivated one allele of a tumour suppressor gene, thus predisposing the patient to develop neuroblastoma. We localized this breakpoint by pulsed field gel electrophoresis, analysis of yeast artificial chromosomes, and fluorescence in situ hybridization. Here we report that the breakpoint is within a large cluster of small nuclear RNA U1 (RNU1) and some tRNA genes (TRE, TRN) on chromosomal band 1p36. The size of this cluster is over two megabases and it contains many other locally repeated sequences. Polyadenylated transcripts were identified for some of these sequences. In addition, the cluster is the target for integration of an adenovirus 5/SV40 hybrid virus. The translocation breakpoint maps distal of this viral integration site and proximal of marker PND.