The concept of washback, or backwash, defined as the influence of testing on instruction, is discussed with relation to second language teaching and testing. While the literature of second language testing suggests that tests are commonly considered to be powerful determiners of what happens in the classroom, Lhe concept of washback is not well defined. The first part of the discussion focuses on the concept, including several different interpretations of the phenomenon. It is found to be a far more complex topic than suggested by the basic washback hypothesis, which is also discussed and outlined. The literature on education in general is then reviewed for additional information on the issues involved. Very little research was found that directly related to the subject, but several studies are highlighted. Following this, empirical research on language testing is consulted for further insight. Studies in Turkey, the Netherlands, and Nepal are discussed. Finally, areas for additional research are proposed, including further definition of washback, motivation and performance, the role of educational setting, research methodology, learner perceptions, and explanatory factors. A 39-item bibliography is appended. (MSE)