Introduction: Our aim was to evaluate the correlation between choroid plexus mass (g) in the choroidal fissure and the ipsilateral interventricular foramen area, bilaterally. Material and methods: We analyzed seven cadaveric specimens with exposed brain, reaching the transcallosum access in all specimens, dissecting the corpus callosum to reach the left and right choroidal fissure. After identifying the thalamostriate and septal veins, we localized the interventricular foramen scrapping all the choroid plexus in that region as well as its posterior extension allowing us to completely visualize the III ventricle. The area of the interventricular foramen was calculated with a pachimeter using the formula πR2. The choroid plexus mass was measured with an appropriate scale. The choroid plexus mass and ipsilateral interventricular foramen correlation was evaluated by the Pearson correlation. Results and conclusion: Neither difference between right and left choroid plexus mass was observed (Student t test – p = 0.374) nor with interventricular foramen area (p = 0.345) and we decided to evaluate the 14 results together. There was correlation between choroid plexus mass and its respective IF (r = 0.6863; p < 0.01). A better knowledge of the choroidal fissure is very important to a more precise approach to the pathologic processes that affect the III ventricle. Different from the transforaminal, interforniceal, subchoroidal, and subforniceal, the choroidal fissure access is a natural approach. We speculate that undetermined etiology hydrocephaly may have its origins in a deficit of ventricular drainage or in the choroid plexus excess.