This chapter covers three main points. The first is that, with respect to null subjects in young children's speech, the data collected thus far indicate no point at which the grammar of U.S. children speaking Standard English (henceforth, American children) clearly licenses null subjects, and no point at which IP and CP are clearly absent. In contrast, the grammars of children acquiring null subject languages do show clear evidence for null subjects and, equally, show evidence at least for IP. This is not to say that no American child ever has an incorrect grammar, but simply that the data thus far give us no grounds for claiming an incorrect grammar for most children. The data are briefly reviewed here.