This critical literature review provides study details for 36 studies examining the effect of glossing for language acquisition among English language learners (ELLs). Useful tables include specificity of participants, gloss types, target vocabulary items and text information about all studies. An analysis of these studies reveals that glossing is an effective means to enhance reading comprehension among ELLs. However, gloss language—whether L1 or English, may depend on learner factors. Other findings include the importance of proximity of gloss to text and the need for glosses that do not require readers to leave the text to access meaning. Considerations such as text genre, text length, targeted items for glossing, number of items to gloss, and gloss presentation are also examined and discussed, including which gloss types may result in trade-offs when glossing is used as a means to promote incidental vocabulary acquisition through independent reading. Several recommendations for further research are offered.