The longitudinal study compared effects of varying amounts of tobacco instruction (one, two, and three years) on the knowledge, attitudes, and behavioral intentions of urban elementary students. A three-year, fourth-through-sixth grade tobacco prevention curriculum was developed based on the Centers for Disease Control and Prevention's Guidelines for School Health Programs to Prevent Tobacco Use and Addiction. The curriculum comprised five, 45-minute lessons per year. The same trained instructor taught the curriculum all three years. Six intervention schools were taught the curriculum, and two control schools were not. A 49-item questionnaire was used to assess tobacco knowledge, attitudes, and behavioral intentions. The experimental group's posttest knowledge and attitude scores were significantly higher than the control group's posttest scores. No significant differences occurred in posttest behavioral intention scores between the control and intervention groups.