The purpose of this study was to investigate whether intentional vocabulary learning, incidental vocabulary learning, or a combination of the two best prepares students for learning and retaining vocabulary in English as foreign language learning (EFL) classrooms. Three experimental groups and three control groups were selected. All groups were given a pre-test and an immediate post-test after the instruction. A delayed post-test was administered to the experimental groups after the immediate post-test. The three experimental groups received the intervention--intentional, incidental, or a combination--while the three control groups received no vocabulary learning instruction. The results show that the mixed instructed group outperformed the other two groups and retained the vocabulary longer than the other groups. Incidental vocabulary learning placed second and intentional vocabulary learning placed third.