Patients with rare overgrowth disorders, such as Beck-Wiedemann syndrome and Simpson-Golabi-Behmel syndrome, are predisposed to embryonal tumours, including Wilms' tumour of the kidney. Therefore, these disorders offer a link between hyperplastic growth and cancer. Genetic lesions at chromosome 11p15 have been associated with Beck-Wiedemann syndrome and Wilms' tumour for several years and the presence of the gene encoding insulin-like growth factor-II (IGF-II) in this region has given rise to much speculation over the involvement of this factor in these growth defects. This speculation was heightened by genetic evidence for the involvement of genomic imprinting in Beck-Wiedemann syndrome and Wilms' tumour, combined with the discovery that the IGF-II gene is imprinted. Although there is a wealth of evidence linking the IGF signalling pathway with overgrowth and cancer, recent progress in the study of 11p15 and developments in our understanding of the mechanism of genomic imprinting indicate that additional imprinted genes located in this region also contribute to these growth disorders.