INTRODUCTION: The small choice of graft materials is one of the greatest problems in femoro-popliteal (F-P) bypass reconstructions. Besides all biosynthetics(2-5) and synthetics(6) graft materials, there is no right alternative for autologous saphenous vein graft in F-P reconstructions. There are two main techniques for F-P reconstructions: "reversed" and "in situ". The aim of this study is the comparison of the long-term patency between "reversed" and "in situ" F-P bypasses. PATIENTS AND METHODS: In the study were included 191 patients with "reversed" and 99 patients with "in situ" F-P bypass grafts operated on between 1988 and 1994. There were 153 (80.10%) male and 38 (19.90%) female patients in the group with "reversed" bypass, and 78 (78.78%) male and 21 (21.22%) female patients in the group with "in situ" bypass. The average age of all patients was 59.04 (27-80) years. Eighty five (44.5%) patients in the group with "reversed" F-P bypass had diabetes mellitus and 43 (43.43%) in the group with "in situ" bypass. One hundred and fifty two (79.68%) patients in the group with "reversed" bypass were cigarette smokers and as 80 (80.8%) in the group with "in situ" bypass. In Table 1 the Fontain classification of occlusive diseases in operated patients is presented. The early proximal reconstructions were performed in 49 patients with "reversed" and 16 patients with "in situ" bypasses (Table 2). The associated proximal reconstructions were performed in 21 patients with "reversed" and in 14 patients with "in situ" bypasses (Table 3). All patients were controlled by physical and Doppler ultrasonographic examination immediately after the operation, after 1, 3, 6 months, and then every year postoperativelly. In cases with suspected graft occlusion or any other complication, control angiographic examinations was also performed. The statistical analysis of the results was done using "Life table" analysis. RESULTS: The patients were followed-up from 3 to 10 years. The results of "life-table" analysis are presented in Tables 4-8 and Graph 1. The "in situ" technique showed statistically significant better long-term patency compared to "reversed" technique, after 2 and 10 years (p < 0.05). The immediate patency in cases with "reversed" bypass was 98.96%, while limb salvage was 97.91%. In the same group long-term patency was 72.8% and limb salvage 73.9%. In the group with "in situ" bypasses the immediate patency as well as limb salvage were 96.97%. In the same group long-term patency was 73.8% and limb salvage 77.2%. In Table 5 potential advantages of the "in situ" F-P bypass technique are shown (16-21). However, there are controversial data on clinical results of both bypasses. Some authors described better long-term results of the "in situ" F-P bypass technique (28-30), while according to other data there are no significant differences between these two bypass groups (31-33). Most authors emphasized the two advantages of "in situ" bypasses in F-P reconstructions: a small diameter of the saphenous vein; in cases with pure run off (34-36).