This article explores the history of the bedwetting alarm, invented in 1938 by two psychologists to cure enuresis, or bedwetting, using the principles of classical conditioning. Infused with the optimism of behaviorism, the bedwetting alarm unexpectedly proved difficult to implement in practice, bearing a multitude of unanticipated complications that hindered its widespread acceptance. Introduced as a medical and psychological technology, in practice the alarm was also a child-rearing device, encouraging the kind of behavioristic attitudes that had prompted its initial development, while simultaneously promoting the child-centered approach that would become dominant in the early 1950s. The life story of the bedwetting alarm muddies the traditional account of how childrearing theories progressed in tidy succession, suggesting both that behavioristic approaches did not die out in the 1930s and that elements of permissive child-rearing were being considered earlier than we traditionally assume.