Praxis and writing of the left hand may be served by different callosal pathways.

A patient who had damage to the leftward outflow of the body of the corpus callosum experienced the development of agraphia, but not apraxia, of the left hand. In another case reported recently, a similar lesion produced the same intriguing dissociation. We suggest that the principal interhemispheric controls for praxis and for writing of the left hand operate at different levels of the corpus callosum.