This study tested two primary hypotheses concerning the effects of mispronunciation on the ratings of source credibility. First, as the number of mispronunciations presented by a speaker increases, audience ratings of source credibility will decrease. Second, the effects hypothesized in the first statement will be stronger for audiences at a more advanced educational level. In addition, the study tested two secondary hypotheses regarding the effects of mispronunciation on the persuasive impact of the message. Following the initial pretest, subjects at two levels of educational background rated the credibility of a speaker who argued for inefficiency in government. There were four versions of the persuasive message, with the number of mispronunications varying in each version. After hearing the speech, all subjects completed the posttest. Analysis of the data provided clear support for the first hypothesis. Other results ran counter to theoretical expectations. (Author/EE)