This study was carried out to assess the effects of intracavitary injection of urokinase in the early liver abscess (ELA) of the rabbits. ELAs were induced on 25 in 47 New Zealand rabbits, which were divided into two groups, with 15 in group A, and 10 in group B. Urokinase was injected into the ELA of group A, and normal physiologic saline into those of group B. One and a half hours after the injections, the rabbits were sacrificed and evaluated by pathologists for the degree of fibrosis of the ELA wall, and fibrinolysis in the ELA itself. Statistical analyses were performed between the two groups. The following ELA sizes for each group were obtained: Group A, 4.3 x 2.9-10.1 x 7.2 mm (mean 7.1 x 4.1 mm); Group B, 4.6 x 2.7-15.0 x 9.7 mm (mean 8.5 x 4.57 mm). Eleven (73%) in group A showed grade II fibrosis of ELA wall, and 8 (80%) in group B showed grade III fibrosis of ELA wall (p=0.002). On pathological analysis, 5 (46%) in group A showed grade II fibrin, and 8 (80%) in group B showed grade III fibrin, of the ELA (p=0.09). In conclusion, injection of urokinase, into the ELAs, can reduce the degree of fibrosis of abscess walls.