Sir Peter Medawar was not only a Nobel prize-winning immunologist but also a wonderful writer about science and scientists. Described by the Washington Post as a `genuinely brilliant popularizer' of science, his essays are remarkable for their clarity and wit. This entertaining selectionpresents the very best of his writing with a new Foreword by Stephen Jay Gould, one of his greatest admirers. The wide range of subjects include Howard Florey and penicillin, J. B. S. Haldane, whom he describes as a `with-knobs-on variant of us all', and, in the title essay, scientific fraud involving laboratory mice. There is Medawar's defence of James Watson against the storm of criticism that greetedthe publication of The Double Helix. A merciless debunker of myths, he reveals the nonsense to be discovered in psychoanalytic interpretations of Darwin's illness and launches devastating attacks on Arthur Koestler, IQ psychologists, and, most notably, Teilhard de Chardin. He raises questions aboutthe nature of scientific endeavour - he famously defined science as the art of the soluble - and a common theme is his desire to communicate the importance of science to the widest possible audience.