Existing research recognizes the critical role of vocabulary in the acquisition of a second (L2)
or foreign language. In the context of L2 writing, it has been established that as vocabulary
size increases, so does the ability to write more effective texts. The purpose of this study
was to investigate the relationship between vocabulary size and ESL students’ written
performance. The participants were 69 Malaysian university students whose writing skills
were assessed as part of their English course requirement. Vocabulary size was measured
using Laufer and Nation (1990) Vocabulary Level Test (VLT). Performance on the VLT
was correlated with writing scores as a measure of written performance. Findings indicated
that a majority of participants achieved a mastery level of the 2000-word test but had
difficulty in the 3000-word and 5000-word level. Participants’ vocabulary size was also
found to be strongly associated with their written performance. These results elucidate the
importance of vocabulary knowledge in L2 writing. The pedagogical implication of the
current work calls for the integration of vocabulary in writing classrooms.