Research suggests that testing (or retrieval) has the potential to enhance second language (L2) vocabulary learning. Given the positive effects of testing, how L2 vocabulary learning from tests can be optimized is an important question. One way to increase the benefits of testing may be to use cumulative tests, where not only recently studied but also previously studied materials are tested. This research compared the effects of cumulative and noncumulative quizzes on L2 vocabulary learning. Seventy-two Japanese university students were randomly assigned to the cumulative or noncumulative group and studied 80 low-frequency English vocabulary items over nine weekly classes. In both groups, participants were introduced to 10 target items in each class and completed a vocabulary quiz in the following class. In the noncumulative group, the 10 items introduced in the previous class appeared in vocabulary quizzes in the following class. In the cumulative group, not only target items introduced in the previous class but also items introduced in earlier classes were tested. Posttest results demonstrate that the cumulative tests may be twice (receptive) or three times (productive) more effective than noncumulative tests. The findings suggest that vocabulary learning can be improved significantly by making simple changes to vocabulary quizzes.