As the world watched the Fukushima reactors release radionuclides into the ocean and atmosphere, the warnings of Dr. Alice Stewart about radiation risk and the reassurances of Sir Richard Doll assumed renewed relevance. Doll and Stewart, pioneer cancer epidemiologists who made major contributions in the 1950s—he by demonstrating the link between lung cancer and smoking, she by discovering that fetal X-rays double the chance of a childhood cancer—were locked into opposition about low-dose radiation risk. When she went public with the discovery that radiation at a fraction of the dose "known" to be dangerous could kill a child, her reputation plummeted, whereas Doll, foremost among her detractors, was knighted and lauded as "the world's most distinguished medical epidemiologist" for his work. Their lives and careers, so closely intertwined, took contrary courses, he becoming "more of the establishment" (as he said), while she became more oppositional. When it was discovered, after his death, that he'd been taking large sums of money from industries whose chemicals he was clearing of cancer risk, his reputation remained unscathed; it is now enshrined in the "Authorized Biography" (2009) commissioned by the Wellcome Institute, along with Doll's denigration of Stewart as an "embittered" woman and biased scientist. Stewart lived long enough to see radiation science move her way, to see international committees affirm, in the 1990s, that there is no threshold beneath which radiation ceases to be dangerous; recent evidence from Chernobyl is bearing out her warnings. But a look at the making and breaking of these reputations reveals the power of status, position, and image to shape scientific "knowledge" and social policy.