This discussion of student output concentrates on reasons for learner's errors, types of errors, and some techniques for correcting them. An error is defined as an unintentional deviation from an expected pattern, which could be a linguistic form, a phonological or a grammatical rule, or an incorrect form or expression in a particular situation. Most errors students make are variable, developmental, and a necessary part of the language-learning process. Generally, such errors can be dealt with in two ways: (1) by building in reviews in the syllabus, and (2) by keeping track of student errors and affording students the opportunity to correct their own errors. It is suggested that whatever method of correction is used, students should understand what the teacher is doing, and why. The method used with children might resemble the way children learn their own language. Methods used with adults would be variable, depending on the situation and the focus of the lesson. (AMH)