This paper examines over 900 why-questions gathered in a longitudinal study of an English-speaking child from 2 to 6 years of age. The child went through a protracted stage in which many why-questions lacked subject-aux inversion, in contrast to other wh-questions. While this asymmetry has been observed in the previous literature, several new observations also emerged. First, the child permitted focus phrases, topic phrases and subordinate clauses to intervene between why and the subject NP in matrix why-questions with no I to C movement. Second, subject-aux inversion was consistently manifested in long-distance questions with tensed embedded clauses, and in utterances with why that were not information-seeking questions. Based on the pattern of data, it is proposed that some children initially permit why to merge high in the left periphery, in SpecIntP, following a proposal for Italian by Rizzi, L. (2001). On the position "Int(errogative)" in the left periphery of the clause. In G. Cinque & G. Salvi (Eds.), Current studies in Italian syntax (pp. 287-296). Oxford: Elsevier. The paper considers whether the child data are best explained (i) by a why-parameter that distinguishes languages permitting merge of why from those languages limited to movement (cf. Ko, H. (2005). Syntax of why-in-situ: Merge into [SpecCP] in the overt syntax. Natural Language and Linguistic Theory, 23, 867-916.), or (ii) as evidence of a universal principle. In the final analysis, the parameter account is preferred, because it explains the individual variation and the sharp transition to the adult grammar that is observed in some children.