Human neuroblastoma cells show at high frequency structural changes of the distal short arm of chromosome 1 (1p). The commonly altered region has been identified in previous loss-of-heterozygosity (LOH) studies to involve deletion of 1p36.1-2. These bands are also the site of constitutional alterations in patients with neuroblastoma. In an approach to define the 1p36.1-2 alterations in more detail we here employ four neuroblastoma cell lines to map translocation breaks involving 1p36.1-2 by fluorescence in situ hybridization (FISH). A chromosomal interval flanked by loci DIS96 and DIS98 contained translocation junctions in each of four lines. This analysis identifies in 1p a restricted genomic region as involved in chromosomal rearrangement in different neuroblastomas. The specificity of neuroblastoma translocation junctions at the molecular level implicates this genomic region in tumor development.