Specificity effects of practice on the classic Stroop color-word task were explored using two different practice tasks, practice on the Stroop task itself and practice on simple color naming. Clear evidence for specificity effects was found, and this specificity persisted across a one-month delay. Stroop practice, but not color-naming practice, led to a pattern of improvement pointing to an advantage for practiced stimuli over unpracticed stimuli on both Stroop and color-naming tests but a disadvantage for practiced stimuli on reading and "reverse-Stroop" tests. The advantage for practiced stimuli was maintained on versions of the Stroop test that used orthographic manipulations of the stimuli. This pattern of specificity is inconsistent with practice as specific to the word forms. It is consistent with practice as specific to colors, to semantic meanings of the words, or to a combination of these two.