Empirical evidence suggests that the study abroad experience accelerates growth in global vocabulary knowledge. The exact nature of this growth is rarely reported, however, and there is little documented evidence to indicate whether it is linear or uneven, whether the speed of growth is constant or changing, or whether the study abroad context favours the acquisition of certain aspects of vocabulary knowledge over others. This paper introduces and evaluates a method of tracking incremental changes in vocabulary knowledge during a year of overseas study. Lexical knowledge is elicited through a word association task completed by the learner at six-weekly intervals. Responses to the task, although not formally constrained, are dependent on the conceptual and lexical associations of the test-taker. Data sets are analysed using a word-knowledge framework, and findings reveal a gradual increase in some aspects of vocabulary knowledge (the number of collocations and native speaker-like associations), but striking inconsistencies over time in others (e.g. word form, form-meaning connections, orthography). The study uses an innovative application of an investigative tool to capture stages in the micro-development of the lexicon, thus exposing the complex and multi-dimensional nature of lexical acquisition. (Contains 10 tables.)