This study investigates when and how French-learning children acquire the main grammatical constraint on the noun category, i.e. the obligatory use of a preceding determiner. Spontaneous speech samples coming from the corpora of twenty children in each of three age groups, 1 ; 8, 2 ; 6, 3 ; 3, were transcribed and coded with respect to morphosyntactic, lexical and length properties of nouns. Results indicate that noun grammaticalization is a gradual process which involves early transitional procedures, as well as an increasing diversity in the content and contexts of determiner use. In support of prosodic hypotheses, noun length effects (in favor of monosyllabic nouns) mostly occurred at 1 ; 8. Animacy effects supporting the lexical hypothesis (in favor of inanimate nouns) occurred at 2 ; 6 and 3 ; 3. We suggest that noun grammaticalization is influenced by both prosodic and lexical factors. Prosodic influences predominate in the first steps of the developmental process, while lexical influences emerge in later steps.