The present study focuses on testing rival hypotheses regarding the effects of advertising readability: Are the effects of readability on cognitive responses and attitudes moderated by the readers' motivation or by their linguistic ability? A two (low/high involvement) by two (strong/weak arguments) by two (low/high readability) factorial design was used to test the hypotheses. The findings support the hypothesis that readers' linguistic ability is the dominant influence factor, because low readability significantly reduces the effects of argument strength under both low and high involvement. Psycholinguistic theory provides explanation for the findings. The implications for advertising practice relate to consumers' levels of literacy. © 2003 Wiley Periodicals, Inc.