The purpose of this study was to determine if students under typical conditions in the American high school English classroom change their attitudes toward and increase their knowledge about American regional and social dialects as a result of being taught a unit in dialectology. The experimental and control groups were comprised of 291 students from two Iowa City high schools. The experimental group was taught a three-week unit in dialectology, while the control group had an individualized reading unit. Participating teachers followed uniform lesson plans, used audiovisual materials prepared for the unit, and kept anecdotal records of their own and students' reactions to various lessons. The students also received a pretest and a posttest. Results indicated that students' attitudes toward and knowledge about dialects did change; on both attitude and knowledge scales, the experimental method was significant in all analyses. It was further indicated that attitudes toward and knowledge about dialects changed as a result of being taught the unit and not because of different teachers, sections, sexes, or IQ scores. (HOD)