In an attempt to identify genes involved in neuroblastoma, we scanned neuroblastoma tumour DNAs for homozygous deletions by representational difference analysis (RDA). The RDA produced several difference products, nine of which represented hemizygous deletions located on chromosome 1 or 3. In order to detect deletions, a genomewide loss of heterozygosity (LOH) screening with polymorphic markers was performed. Allelic losses on a number of different chromosomes were detected, mainly in favourable neuroblastomas (stage 1, 2 and 4S). The most frequently deleted region, apart from 1p, was chromosomal region 3p. A more detailed study was made in this region, which showed that 9 out of 58 (16%) tested neuroblastoma tumours showed allelic loss in the same region on chromosome 3p, i.e. 3pter-14.2. Thus, both RDA and LOH studies showed chromosome region 3p as being frequently involved in deletions and/or rearrangements in neuroblastoma tumours. Therefore, it is possible that one or more of the 3p genes implicated in the development of other cancers also play a role in neuroblastoma development and/or progression.