Potential bidirectional associations between preschool classroom overactive (or externalizing) and underactive (or internalizing) behaviors and language and literacy skills (i.e., vocabulary and listening comprehension) were examined in a sample of children enrolled in Head Start (N = 297). Cross-lagged panel designs using structural equation modeling (SEM) were conducted using data gathered through teacher ratings and direct assessments developed for use in preschool programs serving diverse populations of young children. Significant associations varied by type of behavior and language and literacy skill. Higher overactive behavior in the fall was associated with lower listening comprehension skills in the spring, whereas higher underactive behavior in the fall was associated with lower vocabulary skills in the spring. In addition, lower listening comprehension skills in the fall were associated with higher levels of underactive behavior in the spring. Implications for future research, policy, and practice are discussed. (author abstract)