Neuroblastoma is a heterogeneous childhood tumour of the sympathetic nervous system, in which deletions of chromosomal region 1p and amplification of the MYCN oncogene correlate with aggressive tumour behaviour. However, the majority of neuroblastoma tumours show neither of these aberrations, indicating that other chromosomal regions may be involved in tumorigenesis. Here, we report findings of loss of heterozygosity (LOH) on chromosome 3. In our neuroblastoma material, nine of 59 (15.3%) tested tumours showed allelic loss of chromosome 3p markers. We found significant clinical and biological differences between tumours with the loss of one entire chromosome 3 vs tumours with partial loss in chromosome region 3p. All children with tumours with whole chromosome 3 loss are long-term survivors, whereas all children with tumours showing partial 3p LOH have died from tumour progression. A consensus region found to be deleted in all the tumours with 3p deletions was defined by markers D3S1286 and D3S1295, i.e. 3p25.3-p14.3, distal to the FHIT gene.