This paper will provide a review of research--regarding explicit grammar instruction--that groups recent studies into three main categories and then sub-categorizes these studies under key terms in second language acquisition (SLA) research. The overall purpose of this paper is to argue that in light of these issues, recent studies have shown that explicit instruction in grammar is beneficial in increasing learners' grammatical competence and performance; however, there are learner variables and instructional conditions that influence the extent to which explicit grammar instruction is effective. This paper examines the following: (1) the relationship between explicit and implicit instruction, retention, and types of instructional feedback; (2) studies that reflect the relationship between explicit instruction and the rate and order of developmental sequences; (3) recent studies that discuss various methodologies of grammar instruction in formal classroom settings; and (4) the pedagogical implications, research gaps, and potential orientations for future research on explicit grammar instruction.