The present research study investigated the effects of 8 versions of a computer-based vocabulary learning program on receptive and productive knowledge levels of college students. The participants were 106 male and 103 female Korean EFL students from Kyungsung University and Kwandong University in Korea. Students who participated in versions of the vocabulary learning program with target-word based sentences as well as definitions tended to perform better on receptive and productive vocabulary assessments than those who participated in versions of the program with definitions of words only. Furthermore, results indicated that the difference in receptive scores from immediately after the program to one week later showed a higher drop-rate than the difference in productive scores. In addition, female learners performed receptively better than male learners in post and one-week delayed tests, but significant gender difference failed to occur for the productivity measure. Overall, these results emphasized the importance of productive vocabulary knowledge for better retention of English vocabulary words.