Rowland & Pine (2000) present an analysis of the development of subject–auxiliary inversion in wh-questions in the speech of Adam from the Brown corpus. They show that there is an uninversion period in which the child fails to invert the subject and auxiliary in wh-questions, and they argue that this is a function of the frequency of wh-word+auxiliary collocations in the input: the more frequent a particular collocation is in the input, the more likely it is to be inverted in the child's speech. In this note an alternative analysis is proposed: the initial position of the tensed auxiliary signals interrogative illocutionary force, and the auxiliaries which are most reliably inverted are those that are overtly tensed morphologically. This analysis not only accounts for Rowland & Pine's data but also extends to inversion in yes–no questions. The analysis predicts three different patterns for the development of inversion in both types of questions, and it is shown that all three are attested.