Four patients with severe intraventricular hemorrhage (IVH) were treated using urokinase administered into the lateral ventricles via a ventricular drainage catheter. All patients were female and of ages ranging from 24 to 53 years. The primary diseases were hemorrhagic infarction, moyamoya disease, sinus thrombosis, and thalamic bleeding. Urokinase administration was initiated at 1.3 days average after occurrence of IVH and continued for 3.3 days average in doses of 12,000-96,000 IU per day. Average clot lysis times from IVH, as assessed by computed tomography, were 5.0 +/- 0.8, 5.0 +/- 1.4, and 6.0 +/- 0.8 days for the fourth, the third, and the lateral ventricles, respectively. All patients suffered from meningitis which was probably caused by urokinase administration through a ventricular catheter. However, this was successfully treated by changing the antibiotics. There was no general bleeding tendency or intraventricular rebleeding due to urokinase administration, and none of the ventricular catheters were obstructed by clots throughout the course. The final outcome was good recovery in two patients, severe disability in one, and persistent vegetative state in one. These results correlated well with the consciousness level seen before ventricular drainage in each patient. Consequently, we are convinced that urokinase administration can prevent the harmful effects of IVH and that urokinase is useful not only for lysing ventricular clots but also for maintaining the patency of the ventricular catheter, which is important for control of intracranial pressure in the acute stage of severe IVH.