Previous research had demonstrated diminished interhemispheric Stroop effects in individuals with agenesis of the corpus callosum (ACC), suggesting an important role for the callosum in interhemispheric color-word and color-patch interactions. However, this outcome rested on the results of only 1 ACC participant, who had normal intelligence and a minimum of other neuropathology. In the research reported herein, the role of the corpus callosum in interhemispheric Stroop interference and facilitation was investigated in 9 individuals with complete or partial ACC and normal intelligence, and in non-ACC controls. Congruent, incongruent, or neutral stimulus pairs were presented either unilaterally (color-patch and color-word in the same visual field) or bilaterally (color-patch and color-word in different visual fields). Both unilateral and bilateral (interhemispheric) Stroop interference were found for both ACC and non-ACC groups, with no significant difference in magnitude, indicating that extracallosal pathways are sufficient for mediating this phenomenon. It is suggested that the anterior commissure is a more likely candidate for the interhemispheric transmission of the semantic information resulting in Stroop interference. (JINS, 2001, 7, 302–311.)