This longitudinal study investigated the relation between mothers' descriptions of mental states portrayed in pictures and 2- to 4-year-old children's theory of mind. Mothers described pictures to children at 3 different times during the year. Findings indicated that mothers' use of mental state utterances at early time points correlated with later theory-of-mind understanding. Causality seemed genuine because early theory-of- mind ability was not related to mothers' later mental state utterances. (JPB)