The microanatomy of the lateral sellar or parasellar venous system (so-called cavernous sinus) is poorly understood and is still passionately debated. The exact nature of this venous structure is not yet clear whether it is a plexus or a sinus. In order to understand the anatomy of this area better, an embryological and adult microanatomical study was performed. Serial histological sections of human embryos and fetuses of well determined ages (6, 7, 8, 10, 11, 12, 14, 30 weeks) were used. The adult study was performed with microdissections and serial histological sections of laterosellar compartments. The analysis of this material confirms that the parasellar venous system is a true sinus, on the embryological and histological point of view. They differ from true veins. As other dural sinuses, it may contain different types of channels: from simple venous canal to complex venous plexus. The opinions of different authors are reviewed in the introduction and discussed with the results.