The purpose of this paper is to analyze the role of error analysis in specifying and planning remedial treatment in second language learning. Part 1 discusses situations that demand remedial action. This is a quantitative assessment that requires measurement of the varying degrees of disparity between the learner's knowledge and the demands of the situation. This leads to the qualitative assessment of the knowledge lacking in the learner, as measured against the language of the situation. Part 2 discusses the nature, scope, and problems of error analysis. Of fundamental importance are: a deep analysis of type of error and reasons behind it; an understanding of the process of second language learning; and a description of the learner's model of the target language, as a basis for remedial treatment. A final conclusion is that the study of the learner's model needs refinement, as it can now reveal information only about the learner's code, not about his communicative competence. (AM)