The utmost goal of foreign language instruction is aimed at helping the learner master the language. At the same time the learner shall become equipped with linguistic, pragmatic and social-linguistic competence. This study was done to explore if review activities in EFL classes should be mandatory for learners to learn the new knowledge. One hundred and fifty non-English majors participated in this study. They were divided into three groups, two as experimental groups and one as the control group. Group A received written review treatments whereas Group B received oral review treatments once every three weeks. Group C, the control group, did not receive any review activities. All the participants received a pre-test and a post-test. The results showed that the participants in Group A (written review) and Group B (oral review), performed substantially better than those of the control group. A significant difference in gained scores was found between the control group and the experimental groups, indicating that providing review opportunities is both necessary and helpful for enhancing the learning outcomes. No significant difference was found in review types; both oral and written review methods contributed similarly to the retention of new knowledge. Drawing on the findings, some pedagogical suggestions were made. (Contains 3 tables.)