Perfusion scintigraphy with 99mTc-labeled microspheres was used to assess the integrity of catheter systems implanted in patients with liver metastases for intraarterial regional chemotherapy, and to document the distribution of cytostatic drugs. 33 examinations in 12 patients were performed after implantation as well as prior to each cytostatic cycle. Recurrent stenosis with (3) and without (9) reflux into the adjacent upper abdominal organs was found in each patient with long-term implantation of the port system. In 50% of all cases, the stenosis was successfully treated using urokinase as a thrombolytic agent.