This paper reports on the development of an error-coding instrument and a computerized continuous feedback system for the diagnostic evaluation and remedial treatment of unstructured second-language performances and the use of such a system in an instructional setting. The system does the following: it allows quick, objective, accurate, and detailed evaluation of "creative" written and spoken German; it provides student performance files in the structural and phonological elements of the language that can be updated as required; it allows accurate performance-to-performance comparisons of progress; it permits the instructor to determine quickly the learning status of an individual student, a group of students, or the entire class, and subsequently to design appropriate exercises for that particular target group; and it allows students to judge their performance from the same criteria which were available to their instructor for marking. Feedback procedures and a tabulation of errors for three levels of German language instruction are presented and their systemic implications for the design of pedagogical grammars are discussed. (Author/KM)