There is a fallacy about identifying gifted and talented children and youth that refuses to go away: It is the notion that a single score is "sufficient" for determining giftedness. In this article, the author addresses several reasons for the longevity and ubiquity of this myth, as well as the data that call the myth into question. These include (a) the predictive validity of test scores, (b) the belief that ability is fixed, and (c) the lack of attention to and evidence for other explanations for outstanding achievement. The focus of this article is on the academic domains and IQ, as there are few who argue that a single score predicts performance in the visual and performing arts.