Chronic venous insufficiency (CVI) is estimated to affect 25 million Americans. This condition leads to varicose veins, aching, fatigue, swelling, ulcerations, and bleeding in the lower extremities. The most common cause is a refluxing or incompetent Greater Saphenous Vein (GSV). This condition results in pooling of deoxygenated blood in the lower extremities rather than successful transport of the blood back to the heart and lungs. The historical treatment has been to surgically remove or 'strip' the GSV so that blood is rerouted through the healthier deep veins. A less invasive treatment option, Endovenous Thermal Ablation, has emerged over the last decade and has virtually replaced stripping. This involves advancing a catheter under ultrasound guidance through the GSV and then advancing a laser fiber or radiofrequency probe through the catheter. These devices then produce the energy to destroy the vein as the catheters are slowly pulled back. While both radiofrequency ablation and laser ablation are accepted treatments, neither technology has been definitively proved to have fewer complications or superior results. This is in part because very few practices have the ability to make a head to head comparison between the two technologies and must choose one or the other secondary to financial constraints. The aim of this study is to perform a randomized prospective trial comparing the two modalities so that more definitive information to evaluate complications and outcome can be obtained and then recommendations on which, if either, technology is superior can be made.