In recent years, educators have become ever more aware of the critical role that vocabulary knowledge plays in the academic lives of their students. Vocabulary knowledge is fundamental to the comprehension of text and is most effective when it relates new words to students' existing vocabulary and background knowledge. Effective vocabulary instruction provides multiple exposures through rich and varied activities that are meaningful and relevant to English learning (EL) students (Marzano 2004). This helps them gain ownership and understanding of the words, instead of just learning them well enough to pass a test. Nagy and Scott (2000) noted that "knowing a vocabulary word means being able to do things with it" (p. 273). The principles of effective vocabulary instruction recommended for language arts can be applied to the content area of science. However, science instruction can be especially challenging for EL students who are faced with learning both the language of science and the English language at the same time. EL students are less likely to have the vocabulary needed to comprehend informational text, so instruction that helps build both general academic and content-specific vocabulary knowledge is particularly critical while promoting language development. Even EL students who appear fluent in English frequently need assistance in learning the academic language of science. The goal of this article is to briefly discuss vocabulary instructional strategies and describe how they actively engage EL students in the science vocabulary learning process. Each vocabulary strategy offers students the opportunity to build and extend upon their understanding of a word's meaning and to make personal connections with the science content.