Thrombolysis offers several advantages over surgery in the treatment of thrombosed dialysis access grafts. This study was undertaken to compare the results obtained when thrombolysis was used as the preferred treatment (Thrombolysis Period) for this problem in comparison with the results that had been obtained when surgical therapy had been the preferred treatment (Surgery Period). Each period of study lasted 12 months and the two periods ran consecutively. All data were collected prospectively. No significant problems were encountered when thrombolysis was substituted for surgical therapy as the preferred treatment of thrombosed dialysis access grafts. During the Surgical Period there were 580 thrombotic episodes, a rate of 0.86 per patient. During the Thrombolysis Period there were 568 episodes, a rate of 0.76. These differences were not statistically significant. During the Thrombolysis Period, thrombolysis was found to be as effective as surgery had been during the Surgical Period in the initial treatment of thrombosed grafts. The rate of surgical revision was decreased by two-thirds during the Thrombolysis Period, but the rate of graft replacement was not altered. Long-term patency after therapy by thrombolysis during the Thrombolysis Period was superior to that for surgical thrombectomy performed during the Surgical Period, and was equal to that for revision and graft replacement. The complication rate for thrombolysis was low and complications were managed easily without sequelae. It is concluded that thrombolysis is safe and, when used as the preferred treatment for thrombosed dialysis access grafts, is as effective as surgical therapy. Since it preserves potential vascular access sites and yields long-term patency rates superior to those for surgical thrombectomy, it should be regarded as the treatment of choice for this problem.