Insights from corpus linguistics have come to be seen as having a significant impact in second language pedagogy. Learner corpora, or collections of texts spoken or written by non-native speakers (NNS) of a language, are now being used for the purposes of enhancing language teaching. Specifically, by comparing the corpus of NNS with native speakers (NS) it is possible to identify instances of learners' under- or over-use of spoken vocabulary, as well as to investigate how far, and in what ways learners deviate from NS's norms. This preliminary study compares a small NNS corpus of 43,651 words with an established NS corpus. Results revealed that the Japanese NNS differed markedly in many areas, especially in their underuse of certain lexical items such as discourse markers, modal items, adjectives for specific evaluations, some interactive words, delexical verbs and terms for marking vagueness and hedges. On the other hand, NNS overused some high frequency and auxiliary verbs and some common adjectives. From this data, we suggest that knowledge from learner corpora has important pedagogical implications which include giving higher priority to certain classes of vocabulary including multi-word clusters that appear to be underused among Japanese learners.