This study examines the strength and direction of lexical-grammatical associations within and between first and second languages (l1 and l2) in a longitudinal sample of sequential bilinguals. Thirty-three children who spoke vietnamese (l1) and english (l2) completed picture-naming and story-telling tasks in each language at four yearly intervals. Hierarchical linear modeling across years 1-4 revealed bidirectional within-language associations and a unidirectional cross-language association from the l1 to l2. Results suggest a conditional relationship between languages in which the l1 supports l2 growth, but not vice versa. Findings contribute to defining pathways for l1 and l2 learning across domains and languages. Cambridge university press 2016.