Purpose: As technical development of catheter devices has progressed, endovascular treatments (EVT) for femoropopliteal (FP) lesions have been increasingly employed in patients with peripheral arterial disease (PAD). In the new era of drug eluting stents, the long term patency of EVT for FP lesions are improving, but there are still obstacles in the treatment of complex lesions such as TASC II D, in terms of the long term patency. In order to clarify the prognostic factors of EVT for an extremely long FP lesion, we have retrospectively analyzed clinical data of patients receiving stents with total length >300mm for de novo FP lesions. Methods: A total of 296 de novo FP lesions which were treated by EVT with self-expandable nitinol bare metal stents with a total length greater than 300mm at 13 hospitals in Japan between January 2004 and December 2011 were retrospectively analyzed. Results: Average patient age was 73.9 years (range 50 to 93), and 180 (68.4%) were male. 157 (59.7%) had diabetes mellitus, and 44 (16.7%) were maintained on hemodialysis. 73 (27.8%) were active smokers and 91 (34.6%) were categorized to Rutherford 4, 5, or 6. All lesions were treated with self-expandable bare metal nitinol stents. Average lesion length was 266.3mm and 3.31 stents (range 1 to 6) were deployed, with average total stent length 318.0mm. During the follow-up period (mean 792.9 days), 42 patients died, of which 35.7% were due to cardiovascular disease. Primary patency rates at 1, 3, and 5 years after treatment, respectively, were 68.4%, 47.8%, and 39.1%, and secondary patency rates were 89.5%, 79.4%, and 74.0%. COX proportional hazard regression analyses revealed that male (0.47 [0.31-0.69], p<0.01), chronic total occlusion (2.19[1.05-4.56], p<0.05), calcified lesions (1.52 [1.01-2.30], p<0.05), cilostazol administration (0.60 [0.42-0.88], p<0.01), and stent fracture (2.26 [1.28-3.98], p<0.01), were significant predictors for primary patency. Conclusion: Even though mid-term primary patency rates of EVT for extremely long FP lesions were needed to be improved, secondary patency rates were mostly acceptable. These data will help guide proper treatment strategies for revascularization of complex FP lesions.