Modern linguistic theory offers two main contributions to the improvement of writing: readability and appropriateness. Readability can be developed by improving the correctness of forms used and achieved by carrying out an error analysis on the student's writing to provide insights into errors and clause structure. Linguists have determined that errors may be grouped in two broad classes: mistakes, breakdowns in performance not attributable to competence deficiencies; and defects in competence, correctable by means of a learning program. Students should be helped toward the achievement of "syntactic maturity," exhibiting a wide variety of stylistic devices. Appropriateness, or good style, arises out of a careful consideration of subject, purpose, and audience. Student writing behavior is best changed when passive knowledge, or "competence," is increased and transferred to writing behavior, or "performance." (DF)