Answering yes/no questions (Y/N-Q responding) is a fundamental repertoire in human language and thus it is of both theoretical and practical importance to investigate the origins and development of this repertoire in children and to examine processes whereby it can be trained in populations in whom it does not easily emerge. This article examines research and theory concerning the development and training of Y/N-Q responding in children. Regarding research with neurotypical children, 1 key focus has been biases in Y/N-Q responding at various ages. Younger children tend to show a yes bias, whereas older ones show a bias toward no. Regarding children with developmental delay, there has been relatively little research, almost all of which has focused on children with autism spectrum disorder. In addition, this work has mainly concentrated on using yes/no in the context of the training of Skinnerian operants. After thus considering previous empirical work, the article proceeds to consider theoretical approaches in this area including both joint stimulus control and relational frame theory. These approaches point the way to possible future research in this area.