Two experiments investigated the development of two aspects related to stress assignment in reading. First, we tested whether the role of distributional knowledge concerning stress changes with the development of the reading system; second, we tested whether stress information is computed independently of phonemic information since the first stages of reading acquisition. We ran two identical experiments in Italian, one with children of two age levels (second and fourth grades) and one with adults. Results showed that older children behave similarly to adults, but younger children do not. Differently from the advanced readers, younger children use more general distributional knowledge about stress and are not able to compute stress information apart from phonemes. Taken together, our results suggest that the stress subsystem, and in particular the mechanisms working at the level of the phonological buffer are not fully developed during the first stages of reading.