Introduction The preservation of the great saphenous vein (GSV) has increasingly been considered when surgery for the treatment of varicose veins is indicated when complications from degenerative diseases, such as atherosclerosis at a coronary level and peripheral venous insufficiency occur. Thus, the autologous GSV is considered the best substitute for arterial revascularization. The technique that preserves the great saphenous vein is the Conservative Ambulatory Hemodynamic Management of Varicose Veins (CHIVA), which is widely used. Considering the importance and the use of this technique, the objective of this study was to evaluate the immediate and long-term evolution after surgery on the saphenous vein with the modified CHIVA technique. Materials and Methods A prospective observational study with data from individuals who underwent surgery for the preservation of the GSV by the modified CHIVA technique with the removal of varicose tributaries without ligation of the saphenofemoral junction. Data collection was performed from March 2014 to January 2015 at Padre Anchieta Hospital in Sao Bernardo do Campo, SA£o Paulo. The variables were the great saphenous vein patency assessed by means of vein diameter, as described above, and the presence or not of reflux during the preoperative assessment, on the 30th day after surgery, and at the sixth month after surgery. Results The main results showed that there were no statistically significant differences in the saphenous vein diameter in any of the evaluated segments and in regard to the presence of reflux when comparing the pre-operative period to 30 days after CHIVA and to six months after CHIVA. Conclusion This study did not show change in the diameter of the veins, nor recurrence of reflux in the lower limbs, thus, it showed good results in the short, medium, and long term. There was no relationship between the diameter reductions of veins during the follow-up period.