Conclusion. Visualization of the endolymphatic sac vascular network under video fluorescence microscopy showed a typical microvascular organization. The microvascular arrangement and the microcirculation may reflect a functional state of the endolymphatic sac. Damage or change of the blood circulation following endolymphatic sac surgery is discussed. Objectives. To visualize and study the dynamic microcirculation of the endolymphatic sac in live rats. Method. An experimental animal study using in vivo video fluorescence microscopy. Results. Visualization of the endolymphatic sac vascular network showed a typical microvascular organization. The endolymphatic sac appeared hypervascular and independent from other vascular systems. The microcirculation of the endolymphatic sac was supplied by ramification of a single artery, while venous trunks perpendicular to the length of the endolymphatic sac served as return paths for the microcirculation. The blood flow pattern was highly variable between rats.