The concept of "task" is explored, particularly as it relates to the work students perform in learning a language. It is proposed that what really happens as a student learns can be understood better by applying the concept of task to classroom processes. The ways in which task has been defined by educators are reviewed, and it is concluded that the term reflects three aspects of student work: product; conditions (time, classroom environment, task complexity, student grouping, cooperative learning methodology); and operations (memory, application of principles or formulas, comprehension, opinion). Each of these three aspects is examined further, and the influence of student perceptions on each is discussed. The influence of task type (involving discourse; open/closed; one-way/two-way exchange of information) is also considered. A plan for designing classroom instruction involving five stages is proposed. The stages include: identification of a target task relevant to the whole group; establishing the roles of learners and teachers; selecting input and identifying related skills; creating a pedagogic task; and identifying the desired product. Evaluation of classroom tasks by both students and teachers is also seen as an important element of effective instruction. Contains 102 references. (MSE)