Vocabulary knowledge plays an important role in language learning and language proficiency, but it is difficult to know how much of a role it plays without appropriate vocabulary measures. In this article, we first discuss learner vocabulary in our research on Korean as a second/foreign language. Unable to find appropriate measures for receptive vocabulary knowledge, we undertook the task of developing new tests: Park's "Korean Vocabulary Levels Test" and Delaney's "Korean Vocabulary Knowledge Test." Although we needed to develop new tests from the ground-up, we were able to draw practical insights from (a) the large body of research on L2 English vocabulary and (b) existing tests of vocabulary knowledge tests for L2 English learners. We summarize the design of each test and initial/ongoing validation research. In sum, we have found these tests to have high reliability, generally desirable item statistics, and positive correlations with language skills that largely align with expectations.