The Effect of Vocabulary Size on Reading Comprehension of Iranian EFL Learners

A large number of variables influence the way a learner comprehends a reading passage, one of which is vocabulary size. The studies which have focused on this seemingly important aspect, in some settings, are few and far between. This indicates the importance of running more research in this respect. The present study endeavored to examine this variable to discover its effect on reading comprehension ability of Iranian EFL learners. In so doing, 83 Iranian first-year university students (22 males and 61 females) were given a vocabulary size test (Nation 1990) and a reading comprehension test (TOEFL version 2004). The results showed a very significant correlation between vocabulary size and reading comprehension (r = .84, p < .05), which points out the necessity of improving the learners' vocabulary size in coping with reading passages. However, the high correlation found in this study calls for more replications to add to the precision of such a relationship. Keywords: vocabulary size, reading comprehension, Iranian EFL learners.