If teacher education is to train second language teachers to be principled practitioners, it is essential to resist the attraction of panaceas and recipe-type solutions to instructional problems, and to promote teachers' better understanding of what constitutes successful language learning. Second language acquisition (SLA) research, both applied and theoretical, can play an important role in this process, particularly in the areas of interlanguage and errors, learning vs. acquisition, and learning styles and learning strategies. The SLA component in the training program can be presented in the form of basic training in classroom research or incorporated into an experiential learning cycle in either pre-service or in-service training. In the latter case, trainers play a mediating role. However, teachers and researchers must cooperate to turn theory into practice. Teacher trainers can supply both learners, needed as subjects by researchers, and ideas for useful research; researchers can provide research results to be translated into classroom practice. Such collaboration requires that trainers and researchers understand each others' terminology, possibly through an intermediate literature that makes research accessible to classroom teachers. In addition, more teacher training material on SLA is needed. (MSE)