Previously we found that musicians have significantly larger anterior corpus callosum (CC). In the current study, we intended to replicate and extend our previous results using a new and larger sample of gender-matched subjects (56 right-handed professional musicians and 56 age- and handedness-matched controls). We found a significant gender x musicianship interaction for anterior and posterior CC size; male musicians had a larger anterior CC than non-musicians, while females did not show a significant effect of musicianship. The lack of a significant effect in females may be due to a tendency for a more symmetric brain organization and a disproportionately high representation of absolute pitch (AP) musicians among females. Although a direct causal effect between musicianship and alterations in the midsagittal CC size cannot be established, it is likely that the early commencement and continuous practice of bimanual motor training serves as an external trigger that can influence midsagittal CC size through changes in the actual callosal fiber composition and in the degree of myelinization, which will have implications for interhemispheric connectivity.