Cell competition is a type of short-range cell–cell interaction described in Drosophila melanogaster, in which cells expressing different levels of a particular protein are able to discriminate between their relative levels of that protein in such a way that one of the cells disappears from the tissue (the loser), whereas the other (the winner) not only survives but also proliferates to fill the space left by the disappearing cells. Some tumour-promoting mutations are able to induce cell competition in D. melanogaster, but could cell competition become a target for therapeutic intervention, or early detection, in human cancer?