This experimental study evaluated the effectiveness of direct teaching of new vocabulary items in reading passages. The study compared vocabulary learning under a reading only condition (incidental learning) to learning that is aided by direct communication of word meanings (explicit learning). Three levels of vocabulary knowledge (form recall, meaning recall, and meaning recognition) were assessed using three tests (completion, L1 translation, and multiple choice, respectively). Incidental learning plus explicit instruction was found to be more effective than incidental learning alone for all three levels. The results also showed that direct instruction is especially effective in facilitating the deepest level of knowledge, i.e. form recall. These findings demonstrate the value of the time and effort spent on direct teaching of lexical items in EFL reading classes.