This study investigated the effects of computer educational games on Iranian elementary students' grammar and vocabulary gain. 58 female students ages 13-15 were randomly assigned to experimental and control groups. Both groups received the same classroom instruction, but the experimental group also played grammar and vocabulary games on the computer. Pre- and post-tests were administered and an independent samples t-test found no significant differences between the groups' test scores. However, the experimental group displayed much higher motivation and enthusiasm for learning with the computer games. This implies that computers can significantly increase learner motivation, even if they do not significantly improve test scores.