Abstract The study examines the effect of direct instruction on vocabulary gain through reading texts. Thirty eight intermediate adult learners of English took part in this study. The participants were exposed to two kinds of experimental conditions: reading comprehension (RO) and reading comprehension accompanied by direct instruction of vocabulary (RAD). The Vocabulary Knowledge Scale (VKS) developed by Paribakht and Wesche (1997) was used to measure the participants’ quantitative and qualitative knowledge of target words before and after each treatment. The results of the study revealed that both treatments brought about considerable gains in learners’ vocabulary knowledge but that the RAD treatment resulted in greater gains.

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