Corpus callosotomy was reported for the first time by Dandy in 1922 and developed by Van Wagenen and Herren in 1940, but only Wilson in 1975 started performing it with a microsurgical technique. Its indications have remained controversial for a long time, but during the last years new interest has been raised concerning callosotomy as a treatment for some kinds of generalized epilepsy or as route to the anterior ventricular system. The microsurgical anatomy of the corpus callosum has therefore regained interest. With this goal in mind, the authors studied some aspects of the microsurgical anatomy of the corpus callosum, namely its dimensions, variability and topography, as well as the transcallosal access to the deep interfrontal region and to the third ventricle. This study was carried out on 30 normal adult brains, obtained from routine autopsies, that were submitted to a special preparation procedure and dissected with microsurgical technique. The main aspects of the operating features, the measurements made and the variation in the different parameters are described. Some references are proposed respecting the extent of anterior partial and subtotal callosotomy.