The purpose of this study was to investigate the differences in speech intelligibility and speaking rate for (a) habitual speech, (b) clear speech, (c) alphabet-supplemented speech, and (d) topic-supplemented speech. Eight people with severe dysarthria following traumatic brain injury participated in this project. Speakers were video recorded as they produced ten sentences under each of the four conditions. Five listeners transcribed each of the speech samples. The alphabet-supplemented speech intervention yielded significantly larger higher observed intelligibility scores than habitual speech, clear speech, topic-supplemented speech, or alphabet-supplemented habitual speech.