Neuroblastoma is a childhood tumour of the sympathetic nervous system that demonstrates striking clinical heterogeneity. In order to determine which genes are abnormally expressed in neuroblastoma, we screened regions of amplification from the short arm of chromosome 2 in the neuroblastoma cell line IMR-32 and found that the homeobox gene, myeloid ecotropic integration site 1 (MEIS1), is highly amplified. MEIS1 normally maps to chromosome band 2p14. High expression of MEIS1 without amplification was also found in other neuroblastoma cell lines, with and without MYCN amplification, and in medulloblastoma and crythroleukaemia cell lines. MEIS1 is highly expressed in cerebellum and ubiquitously expressed in normal immunohaematopoietic tissues and is thought to be important in cell proliferation and differentiation. While several lines of evidence point towards a role for homeobox genes in the development of other malignancies, this is the first report showing the amplification of a homeobox gene in neuroblastoma.