OBJECTIVE To study the fluorescein angiographic appearance of the extreme peripheral retina in patients with proliferative diabetic retinopathy with rubeosis iridis. METHODS Using a modified endoscope, fluorescein angiography was performed prospectively during pars plana vitrectomy on 14 eyes of 12 patients with proliferative diabetic retinopathy who had or developed postoperative rubeosis. These findings were compared with those obtained from 41 eyes of 35 patients without rubeosis. RESULTS A fibrovascular ridge was observed at the ora serrata in 11 of 12 eyes (92%) with rubeosis but in only 15 of 35 (43%) eyes without rubeosis. Seven of 12 (58%) eyes with rubeosis showed the continuous type of fibrovascular ridge, whereas only 5 of 35 (14%) eyes without rubeosis showed the continuous type. A broom-shaped continuous fibrovascular ridge was observed only in eyes with rubeosis. CONCLUSIONS Many eyes with proliferative diabetic retinopathy showed unusual findings in the extreme retinal periphery, which were more frequent in the eyes with rubeosis iridis. Fluorescein angiography of this region may provide valuable information for possible anterior neovascularization.