Deregulation of imprinted genes has been observed in a number of human diseases such as Beckwith-Wiedemann syndrome, Prader-Willi/Angelman syndromes and cancer. Imprinting diseases are characterised by complex patterns of mutations and associated phenotypes affecting pre- and postnatal growth and neurological functions. Regulation of imprinted gene expression is mediated by allele-specific epigenetic modifications of DNA and chromatin. These modifications preferentially affect central regulatory elements that control in cis over long distances allele-specific expression of several neighbouring genes. Investigations of imprinting diseases have a strong impact on biomedical research and provide interesting models for function and mechanisms of epigenetic gene control.