Despite the recent progress in vitreous surgery, treatment of proliferative vitreoretinopathy (PVR) is still difficult. Even if the reattachment of the retina is successful, visual prognosis is often unsatisfactory. Identification of clinical risk factors for PVR provides useful guidelines for planning the management of rhegmatogeneous retinal detachment. This review summarized the current concept for pathogenesis, clinical risk factors, and medical treatment for PVR. The presence of retinal breaks and the breakdown of the blood-retinal barrier are prerequisite to development of PVR. Almost all risk factors for PVR are associated with intravitreal dispersion of retinal pigment epithelial cells or the breakdown of the blood-retinal barrier.