Recently, the notion of genre has been reconceived as social action, or as typified rhetorical response to recurring situations (Miller, 1984), and this reconception has been used to illuminate the varieties of school writing as well as professional and workplace discourse. A natural question that emerges from this theory and research has to do with how teachers might best use this new knowledge. Specifically, can the explicit teaching of genre features and rules enhance or facilitate the acquisition of such genres by students? Two tentative answers are offered to this question: Each is based both on the relevant research that is currently available (my own and that of others) as well as on current disciplinary knowledge about first-language acquisition, writing development, and second-language acquisition. The Strong Hypothesis states that explicit teaching is neither necessary nor useful (if even in fact possible); the Restricted Hypothesis allows for certain carefully specified exemptions to this general principle. Ultimately, in both its form (by offering two hypotheses) and in its substance, this paper is a plea for more focused research and theoretic consideration of this question.