Fifty-six children were observed longitudinally from 18 to 30 months of age interacting with their mothers during a Communication Play that contained 8 scenes designed to encourage interacting, requesting, commenting, and narrating. Of primary concern was how often symbols infused the child's states of engagement with people and objects and how experience in such symbol-infused states related to language acquisition. Findings indicate that symbols increasingly infuse joint engagement, and that both the timing and the trajectory vary widely among typically developing toddlers, especially during the last half of the 2nd year. Moreover, variations in amount of symbol-infused supported joint engagement may both be influenced by variations in the onset of language and contribute to differences in language facility at 30 months.