OBJECTIVE: Frame-based stereotatic catheter placement and subsequent thrombolysis is one treatment option for the management of a deep intracerebral hemorrhage. Recently, frameless stereotactic surgery with a navigation system has been introduced to reduce the hematoma volume. This study was designed to evaluate the effectiveness of frameless stereotactic ICH catheterization using a navigation system. METHODS: From January 2006 to November 2006, we identified 27 patients who were diagnosed with deep ICH and underwent navigationassisted frameless stereotactic catheter insertion with/without thrombolysis by urokinase irrigation. RESULTS: The mean length between the center of the hematoma and the tip of the catheter was 6.8 mm (range between 0 and 15 mm). The catheter tip and target matched in 8 patients (29.6%). In cases of an inappropriately located catheter tip (70.4%), most of the hematomas were thalamic in location due to the long trajectory (9 of 10 thalamic locations). The preoperative hematoma volume showed a statistically significant correlation with the final hematoma volume. There was no mortality reported. Multiple regression analysis showed a statistically significant correlation between the initial Glasgow coma scale score and the outcome. CONCLUSIONS: Navigation-assisted frameless stereotactic ICH catheterization has limited accuracy but is effective in reducing the ICH volume reduction.