Effects of anticoagulant or fibrinolytic therapy on anterior chamber fibrin following cataract surgery was evaluated. In one series of experiment, various amounts of antithrombin III (ATIII), an anticoagulant, were injected into the anterior chamber of the rabbit eye immediately after phacoemulsification of the lens. In another series, various amounts of tissue plasminogen activator (TPA), a fibrinolytic agent, were injected into the anterior chamber 24 hours after phacoemulsification when it was filled with fibrin. The extent of the fibrin clot was graded using a slit lamp microscope, and the aqueous flare intensity was determined with a laser cell-flare meter for 2 weeks after operation. The eyes treated with TPA was also examined with light and electron microscopy. ATIII showed an inhibitory effect on fibrin formation, but complete inhibition was not obtained even with the highest concentration used. In contrast, the fibrin clot was completely resolved even with the lowest dose of TPA used, while no side effect such as inflammation or bleeding was seen. Histological examinations revealed no pathological changes in eyes treated with TPA. TPA may be a promising agent for fibrin resolution after cataract surgery.