Knowledge of word meanings and the ability to use words are fundamental to nearly every interaction of every day. Beginning long before formal schooling, vocabulary skills underpin many aspects of communicative, social, and academic well-being. Thus, evaluation of vocabulary knowledge and use is central to any complete assessment of language proficiency. We have advanced in our use of vocabulary assessment significantly since Binet and Simon first used vocabulary tests to measure cognitive proficiency. We have a repertoire of informative tools and strategies from which vocabulary assessment protocols can be fashioned. Current assessment approaches integrate multiple sources of information. They also look beyond existing word knowledge toward word-learning potential. Integrated and dynamic approaches can provide a rich way to ascertain young children's vocabulary abilities and aptitudes.