The research foundations for understanding strategies of second language learning are outlined. Three research themes are highlighted: the importance of second language learning strategies, the effectiveness of strategies as demonstrated by research, and the definition and classification of these strategies. Second language learning strategies are important because they improve language performance, encourage learner autonomy, are teachable, and expand the role of the teacher in significant ways. Information on the effectiveness of language learning strategies has been gathered by a variety of means, including simple list-making, observations by teachers and researchers, interviewing, notetaking and diaries by students themselves, self-reporting surveys, factor analytic studies, and training studies involving experimental and control groups. Each of these ways of determining the utility of second language learning strategies is discussed, and a new and more complete taxonomy of second language learning strategies based on a comprehensive review of research is presented. (Author/MSE)