This study investigates the acquisition of the discourse/pragmatic notion of topic, based on an experimental task eliciting topic vs. focus subjects. In spoken French, these are obligatorily realized as dislocated vs. nondislocated noun phrases. The results provide overwhelming evidence for the early mastery of topic, even by the youngest children (2;6). The only difficulty was in the evaluation of fine-grained salience distinctions, leading to the underuse of full noun phrases in ambiguous contexts. A theory of mind test revealed that the ability to assess their listener's knowledge state is not sufficient to explain this underuse. Instead, children's overreliance on the situational context as a source of complementary information to disambiguate their utterances is argued to have a major impact on how explicit they are. (Contains 6 tables, 2 figures, and 11 footnotes.)