The assessment of so-called depth of word knowledge has been the focus of research for some years now. In this article the construct of deep word knowledge is further specified as the decontextualized knowledge of word meanings and word associations. Most studies so far have involved adolescent and adult second language learners. In this article, we extend the focus to younger first and second language learning children in primary school in the Netherlands. A well-established test format involving word associations has been adapted for this younger target group and the feasibility of assessing deep word knowledge in primary school children is evaluated empirically. The results showed that the test provides a reliable and efficient method of assessing the children's vocabulary knowledge. Evidence of validity was obtained from a concurrent definition task, and from an analysis of the scores in terms of language background, which is known to be associated with different levels of vocabulary knowledge. (Contains 1 figure, 6 tables, and 9 footnotes.)