David Baulcombe has discovered a new level of gene regulation, RNA silencing, and the small interfering RNAs that mediate it. Although he has always worked with plants and their viruses, the fundamental principles that he has discovered have been shown to apply equally to animal cells with profound consequences for biological sciences and now for medicine. For these reasons he was invited to deliver the Academy’s Jean Shanks Lecture in 2008. Silencing by siRNA has become an essential tool in all branches of biological sciences and it is becoming increasingly clear that changes in microRNA profiles are extremely important in a range of human diseases, especially cancer. There is growing evidence that changed microRNA profiles contribute to cancer and that these changes can provide both diagnostic and prognostic information. David Baulcombe’s discoveries have been very widely recognized, including election to the Royal Society and Foreign Membership of the National Academy of Sciences of the USA, the Lasker Prize, the Benjamin Franklin Medal, the Massry Prize, the Wiley Prize, the Royal Medal of the Royal Society and a knighthood. David Baulcombe’s election to the Academy would bring breadth and exceptional expertise in a rapidly emerging area of increasing medical importance.