In a preliminary clinical study, recombinant tissue plasminogen activator (rt-PA) was injected into the anterior chamber of 18 eyes and into the vitreous cavity of 2 eyes in a total of 20 patients. The clinical indications were severe fibrin formation after filtering operations for glaucoma (8 eyes), diabetic neovascular glaucoma (3), fibrin and hemorrhage after vitrectomy (3), keratoplasty (3), posterior chamber lens implantation (1), trauma (1), and endophthalmitis (1). Complete fibrinolysis within a minimum of 2 h was achieved in 81% of 26 injections. Although doses of about 12 micrograms rt-PA were generally given, in our observations, 6 micrograms proved to be sufficient for rapid fibrinolysis in selected cases. Injections of rt-PA should not be considered before the 3rd postoperative day so as to avoid rebleeding and recurrent fibrin formation. No toxic intraocular side effect was observed after the use of rt-PA in this study.