In a longitudinal study we investigated 5th- and 7th-grade children's perceptions of smokers and nonsmokers, changes in perceptions from 5th to 7th grades, and the degree to which these perceptions predict smoking in 9th grade. The participants were 1,663 students from 14 school districts in Washington state. The results showed large developmental shifts from 5th to 7th grade in children's perceptions of both smokers and nonsmokers: Students at 7th grade saw smokers in a much more positive light and nonsmokers in a much more negative light than they did at 5th grade. Children's positive perceptions at 5th grade of smokers predicted smoking 4 years later at 9th grade and were stronger predictors than positive perceptions at 7th grade. The results suggest that smoking prevention interventions must begin before 5th grade to counter perceptions predictive of subsequent smoking.