Professor Peter Scambler is Professor of Molecular Medicine at the Institute of Child Health, Great Ormond Street, London. His first important research contributions were in the field of cystic fibrosis genetics. His group was the first to identify submicroscopic deletions as the major cause of DiGeorge and velo-cardiofacial syndromes. This discovery initiated a new area of research, as the small chromosome 22 deletion is the most common interstitial deletion in man, found in 1:4000 live births, and turns out to be associated with other abnormalities, such as congenital heart disease. He has successfully characterised the molecular basis of a series of other important birth defects.