The assumptions underpinning grammatical mistakes can often be detected by looking for patterns of errors in a student's work. Assumptions that negatively influence rhetorical effectiveness can similarly be detected through error analysis. On a smaller scale, error analysis can also reveal assumptions affecting rhetorical choice. Snags in the students' actual composing activity can also be spotted through error analysis. Grammatical correctness or rhetorical effectiveness cannot be evaluated without considering the activity that presented the grammatical or rhetorical form as a possible solution to the problem of making a meaningful statement. The primary reason the cognitive activity must be considered is that remediation of incorrect or ineffective structures depends upon changing that activity and upon altering the assumptions producing the miscues. Since error analysis can evaluate miscues involving literal, textual, and contextual meaning and offer suggestions concerning how to improve a writer's individual composing procedure, it should be considered as a process-oriented method of evaluating both the composing process and its products. (HOD)