The great saphenous vein (GSV) is unusable in 20% of cases. The best alternative in these cases is the GSV of the contralateral lower limb (CLL). However, many surgeons are reluctant to harvest the contralateral GSV for fear that it might be needed for future treatment of critical ischemia in the CLL. The purpose of this retrospective study was to observe the long-term behavior of the CLL and to identify prognostic factors for the development of critical ischemia as a basis for contraindicating harvest of the contralateral GSV. The study was conducted in patients who underwent distal bypass for trophic manifestations between January 1995 and December 1997. Patients who had a history of contralateral bypass using the GSV or major amputation were not included. Eighty-one of the 86 patient records could be analyzed with a minimum follow-up of 5 years. Survival was 59% and 40% at 2 and 5 years, respectively. Statistical analysis focused on age, risk factors, trophic manifestations on the CLL, ankle-brachial index, and arteriographic findings. After 5 years of follow-up, seven of the 81 patients (8.6%) required contralateral long bypass. Presence of contralateral trophic manifestations at the time of initial bypass was the only statistically significant prognostic factor for requirement of contralateral long bypass (p < 0.01). These findings support harvesting of the contralateral GSV for lower limb salvage. The risk that long contralateral bypass will be required is low except in patients with contralateral trophic manifestations.