People frequently make assumptions about others because of their spoken or written use of a particular dialect or language. The varieties of English that people use are often regarded as indicators of corresponding intelligence, competence, motives, and morality. Such assumptions--frequently based on myths and misconceptions about the nature of language--can lead to discriminatory practices. Literacy educators should work to combat prejudice by dispelling linguistic myths and working with students to expose and critique the processes and institutions that perpetuate such misconceptions. This article outlines and critiques common myths that contribute to language-based discrimination. These myths include misunderstandings about grammar and usage rules, misinformed beliefs about particular language varieties as "random" rather than rule governed, and misconceptions about how to judge the relative value or quality of specific language varieties. In addition, the author suggests activities that encourage learners to investigate the actual nature of linguistic diversity and to question the ways that linguistic prejudice is propagated institutionally.