In the previous studies, we found that lumbrokinase an, extract from Korean earthworm, had a strong in vitro thrombolytic effect, and that when added to thrombin had a significant effect in reducing fatality rate in thrombin-induced lung infarction mice model. To determine whether it also has in vivo thrombolytic effect in cerebral embolism model using 9 Spraw Dawly male rats of 200 to 300gm, we cannulated the extemal carotid artery lene tubes and occluded the pterygopalatine arteries. Via the extemal carotid artery, we injected 1 mm3 of human blood clots which were previously mixed with Tc-99m sulfur colloid. After confirming the intracranially situated clot by camera, we injected 3cc of following fiuids to each group of three rats: saline, urokinase, lumbrokinase fraction m Then using Gamma camera of 64*64 m obtained for 1 minute in every 30 minutes. After 150 minutes radioactivities of the clots in the brain were 3.02%, 21 02% urokinase, and lumbrokinase treated animals respectively. In the liver, the uptake of radioactivities was accordingly increased. Brain sections showed no Significant intracranial bleeding in any of the treated animals. Therefore, we conclude that lumbrokinase has in vivo thromboembolism model without producing significant intracranial bleeding. However, compared with its in vitro effects the in vivo effects appear to be less potent. Futher experiments with better designed animal models are warranted.