Sclerosant microfoam is composed of microbubbles of room or air carbon dioxide (CO(2)). When air is mixed into the surfactant liquid sclerosant, microbubbles of reduced diameter can be obtained of sufficient stability to be injected into the vessels. The area of liquid on the surface is enormously increased in inverse proportion to the diameter of the bubble. Polidocanol in microfoam form displaces the blood from the vessel, permitting homogeneous contact between the sclerosant and the endothelium and facilitating endothelial destruction, and is visible in real time by ultrasonography. The concentration and volume of microfoam can be adjusted according to the disease treated. In the case of home-made foams, however, the volume of gas that can be injected is limited by the low solubility of nitrogen, and only the concentration can be modified. CO(2) is a nontoxic and highly soluble physiological gas, and large amounts can be administered. Here, we report the technique and long-term outcomes of ultrasound-guided injection of polidocanol microfoam in the treatment of large varicose long saphenous veins, postsurgical recurrence varicose veins, varicose ulcers, and venous vascular malformations.