Foreign language learning is a challenging task, involving mastering a new sound system, phonological and syntactical forms, vocabulary, and sometimes a new writing system. For the adult second language learner, one of the most frustrating aspects is having an inadequate vocabulary for expressing complex ideas that are so easy to relate in one's native tongue. The acquiring of new vocabulary becomes one of the most important tasks as one strives for fluency in the second language. This research provides brief overview of how computers have been used and are being used for language learning. The present research also explores the effects of CALL on vocabulary learning. It discusses the use of the computer for lexical skill development in relating CALL to vocabulary acquisition via an experimental method and searching for effective ways to use CALL in vocabulary instruction. The results indicate that in using CALL program, learners have an intensive mental processing which results in long term recall of words. CALL also produced better results in contextualized vocabulary learning, plus better pronunciation. However, the results show that in the first experiment the scores on the immediate test were considerably higher for the control group, but the scores on the delayed tests were significantly lower for the control one.