I observe that in an earlystage of child Catalan and Spanish, no overt subjects are used. At this same age and MEAN LENGTH OF UTTERANCE (MLU), child speakers of overt subject languages such as French, German, Dutch, and English use at least some overt subjects optionally. I explain this crosslinguistic variation bysuggesting that the adult target grammars vary with respect to the position in which overt subjects are realized. In the overt subject languages, subjects are realized in the canonical specifier-of-IP position, whereas in the null subject languages (such as Catalan and Spanish), subjects are located in a topic/focus position, which becomes accessible onlylater in development. As evidence for this, I show that overt subjects, fronted objects, and WH-questions begin to be used at the same point in development in child Catalan and Spanish. I also argue that subject agreement constitutes an incorporated pronominal subject in Catalan and Spanish and that children converge on this parametric option veryearly . The inabilityof child Spanish- and Catalan-speakers to use discourse-pragmatic information is explained as a delayin the development of the interface between grammar and discourse-pragmatics.