To evaluate the efficacy and safety of a silicone oil-RMN3 mixture ("heavy silicone oil") as heavier as water internal retinal tamponade after vitrectomy for complicated retinal detachment. The relative density of the heavier-than-water silicone oil was 1.03 g/cm3, and the viscosity was 3,800 cSt. Heavy silicone oil is designed to tamponade the inferior retina in complicated retinal detachment. Patients with a complicated retinal detachment involving the inferior part of the retina requiring internal tamponade with silicone oil were recruited for this prospective study. Inclusion criteria were retinal detachment secondary to proliferative vitreoretinopathy (stage > or = C2), inferior or posterior tears, or penetrating trauma. The heavy silicone oil was injected at the end of surgery after peeling of retinal membranes or retinotomy. Follow-up examinations were scheduled at 1, 3, 6 months, and 1 year after the initial surgery. A total of 33 eyes of 33 patients aged from 20 to 84 years (mean, 56 +/- 18 years) were treated with heavy silicone oil. Follow-up ranged from 12 to 16 months. Rhegmatogenous retinal detachment with significant proliferative vitreoretinopathy accounted for 17 cases, inferior holes for three, and trauma with retinal detachment for three. Initial visual acuity ranged from 20/50 to hand motions. Initial retinal reattachment was achieved in all cases. Complications included increased intraocular pressure in six eyes (18%), intraocular inflammation and synechia formation in one eye (3%), a central retinal artery occlusion after heavy oil removal in one eye, and scattered retinal hemorrhages during follow-up in two eyes (6%). Significant emulsification was not observed during intraocular tamponade with heavy silicone oil. At the last follow-up, all eyes had macular attachment, and 24 eyes had a visual acuity better than or equal to 20/400. The results of this prospective study show the good intraocular tolerance of heavy silicone oil as tamponade in complicated retinal detachment. Its specific gravity allows for sufficient tamponade of inferior retinal tears for at least 3 months without significant side effects.