OBJECTIVE We studied the immediate and long-term efficacy of the Wallstent device in the treatment of ureteral obstruction caused by malignant disease. METHODS In 23 patients (30 ureters), self-expanding metal stents were implanted endoscopically (n = 23), percutaneously (n = 5), or bidirectionally (n = 2) because of extrinsic malignant ureteral obstruction. Patients who met the following criteria were selected for stent implantation: (1) life expectancy of at least 6 months, (2) current polychemotherapy, (3) increasing levels of serum creatinine, and (4) severe clinical signs and symptoms associated with hydronephrosis. Obstruction was diagnosed by using sonography and excretory urography. After radiologic localization and dilatation of the stenosis, the Wallstent device was inserted. For 4 weeks, a double-J catheter inserted through the stent was kept in place in order to prevent obstruction by reversible hyperplastic reaction of the urothelium. Patients were followed up for 31 weeks (range, 3-75 weeks). Follow-up included sonography, excretory urography, and determination of serum levels of creatinine in all cases and furosemide scintigraphy and the Whitaker test in selected cases. RESULTS Implantation of the Wallstent device was successful in 30 (97%) of 31 cases attempted. The survival rate was 81% after 6 months and 61% after 8 months. The primary patency was 83% after 30 weeks. Complications were macrohematuria (one patient) and incrustation (two patients). No infection and no migration or compression of the stent were observed. CONCLUSIONS Implantation of a Wallstent device is a safe and effective alternative to double-J catheter placement in tumor-associated ureteral obstruction.