This article investigates the origins of the "eventivity effect" during the root infinitive (RI) stage in child French, German, Dutch, and English. Ferdinand (1996), Wijnen (1997), Hoekstra and Hyams (1998), and Becker and Hyams (2000) show that children acquiring French, German, and Dutch (F/G/D) use almost exclusively event-denoting predicates as root infinitives (RIs). By contrast, stative verbs in these child languages have been shown to appear in a finite form. Hoekstra and Hyams (H&H) (1998) argue that the eventivity effect stems from modal/irrealis semantics of infinitival predicates, a morphological predicate type that occurs in adult and child F/G/D root clauses. H&H also propose that the RI stage in child English does not manifest the eventive/stative distinction because bare stems (the most frequent nonfinite predicate type) are inherently [+perfective] (Giorgi and Pianesi 1997). The main objective of this article is to provide an alternative analysis of the eventivity effect and to show how it is present in all four languages (F/G/D and English), contrary to what H&H suggest. The central claim is that the eventivity effect results from the under specified nature of AspP, a projection where eventives with no inherent telicity pick up an appropriate syntactic telicity feature. The new account eliminates the distinction between the two types of RI grammar (the F/G/D type and English type) suggested in the work of H&H because it attributes the occurrence of RA to the same property of child grammar. The article also discusses the implications of the proposed analysis for cross-linguistic variation in the RI stage.