This study investigated predictors of growth in toddlers' vocabulary production between the ages of 1 and 3 years by analyzing mother-child communication in 108 low-income families. Individual growth modeling was used to describe patterns of growth in children's observed vocabulary production and predictors of initial status and between-person change. Results indicate large variation in growth across children. Observed variation was positively related to diversity of maternal lexical input and maternal language and literacy skills, and negatively related to maternal depression. Maternal talkativeness was not related to growth in children's vocabulary production in this sample. Implications of the examination of longitudinal data from this relatively large sample of low-income families are discussed.