The value of language learning theory and research is discussed, and the need for content-related linguistic, sociolinguistic and cultural research, as well as treatment-related research on language teaching and learning, is emphasized. It has been only gradually, from about the mid-sixties and increasingly from the early seventies, that second language learning has begun to be consistently researched. This research has been prompted by the psycholinguistic interest in language acquisition, the linguistic interest in the characteristics of learner languages, and the "applied" interest in the improvement of second language teaching and learning. Current research efforts are cited. As an orientation for research, and as an aid for teachers and learners, a model of the language learner and language learning is offered. Six main categories are identified in the model: context, learner, teaching input, opportunities to use the second language in the environment, the learning process, and the learning outcome. (SW)