The efficacy of a reinforced biosynthetic ovine collagen (RBOC) vascular prosthesis developed for small arterial reconstruction was assessed by examining 30 grafts in 29 patients with arteriosclerosis obliterans. The operative procedures performed were femorofemoral bypass in 2 patients, above-knee femoropopliteal bypass in 28 patients, and below-knee femoropopliteal bypass in 1 patient. Femoropopliteal bypass was simultaneously performed in two patients undergoing femorofemoral bypass using one or two grafts. The indications for surgery were intermittent claudication in 27 patients and to salvage the limb in 2 patients. The longest follow-up period was 49 months, and there were six graft failures, occurring 1, 1, 9, 17, 17, and 23 months after implantation, respectively; caused by compression of the graft from outside in two, infection in one, anastomotic intimal hyperplasia in one, and unknown factors in two. Thus, the primary cumulative patency rate for above-knee femoropopliteal bypass at 3 years was 83.7%, and the secondary patency rate was 91.2%. No aneurysmal change was observed. Moreover, the RBOC was able to be used without preclotting, and its handling and suturing characteristics were satisfactory. Our findings suggest that this vascular prosthesis may be an acceptable alternative for above-knee femoropopliteal bypass.