This study investigated the relationship between grammatical errors and communication breakdown by examining native speakers' ability to correct grammatical errors. The assumption was that communication breakdown exists to a certain degree if a native speaker cannot correct the error or if the correction distorts the information intended to be conveyed by the writer. The variables examined in the experiment were two grammatical items, namely articles and connecting words between clauses; three types of errors: omission, insertion, and wrong choice; and two passages. The subjects, 120 graduate students, all native speakers of English, corrected the texts that were mutilated in one of six different ways for one of two different passages. The results indicated that mutilation of articles was easier to correct than connectors for omission and wrong choice, but not for insertion type errors. These findings can be generalized over different kinds of passages when a synonomous scoring rule is used but not when a verbatim rule is used. Generally, the findings have implications for the assessment of comprehension as measured by cloze procedure and for the assessment of writing competence. (Author/AMH)