Successful catheter-directed thrombolysis (CDT) for iliofemoral deep vein thrombosis (IFDVT) reduces post-thrombotic morbidity and is a suggested treatment option by the American College of Chest Physicians for patients with IFDVT. Pharmacomechanical thrombolysis (PMT) is also suggested to shorten treatment time and reduce the dose of plasminogen activator. However, concern remains that mechanical devices might damage vein valves. The purpose of this study is to examine whether PMT adversely affects venous valve function compared to CDT alone in IFDVT patients treated with catheter-based techniques. Sixty-nine limbs in 54 patients (39 unilateral, 15 bilateral) who underwent catheter-based treatment for IFDVT form the basis of this study. Lytic success and degree of residual obstruction were analyzed by reviewing postprocedural phlebograms. All patients underwent bilateral postprocedure duplex to evaluate patency and valve function. Phlebograms and venous duplex examinations were interpreted in a blinded fashion. Limbs were analyzed based on the method of treatment: CDT alone (n = 20), PMT using rheolytic thrombolysis (n = 14), and isolated pharmacomechanical thrombolysis (n = 35). The validated outcome measures were compared between the treatment groups. Sixty-nine limbs underwent CDT with or without PMT. The average patient age was 47 years (range, 16-78). Venous duplex was performed 44.4 months (mean) post-treatment. Of the limbs treated with CDT with drip technique, 65% demonstrated reflux vs 53% treated with PMT (P = .42). There was no difference in long-term valve function between patients treated with rheolytic and isolated pharmacomechanical thrombolysis. In the bilateral group, 87% (13/15) demonstrated reflux in at least one limb. In the unilateral group, 64% (25/39) had reflux in their treated limb and 36% (14/39) in their contralateral limb. There was no correlation effect of residual venous obstruction on valve function, although few patients had >50% residual obstruction. In patients undergoing catheter-based intervention for IFDVT, PMT does not adversely affect valve function compared with CDT alone. A higher than expected number of patients had reflux in their uninvolved limb.