Human recombinant tissue plasminogen activator (25 micrograms) was injected into seven eyes of six patients who had developed massive fibrin deposition after vitrectomy surgery for diabetes. Six eyes had developed pupillary membranes and recurrence of tractional retinal detachment from fibrin membranes, and one eye had developed only a pupillary membrane. All pupillary membranes resolved within one hour of administration of tissue plasminogen activator, and five tractional retinal detachments resolved within 24 hours. All eyes developed evidence of intraocular bleeding after tissue plasminogen activator injection. Subsequently, six of seven eyes developed recurrence of fibrin accumulation and tractional retinal detachment.