Stroop interference is often explained by an automaticity account, according to which it arises due to more extensive practice in reading than in color naming. Here we investigated the effect on interference of isolated practice in color naming (of incongruent and neutral stimuli) and in word reading (of color names) in adults and children in Grades 4–5. In both groups interference was reduced after practicing color naming of incongruent stimuli. For children, interference was also reduced after practice in word reading of color names. In neither group was interference diminished after practice in color naming of neutral stimuli. These findings are consistent with a negative relationship between reading ability and interference and challenge the automaticity account.