Purpose: Klippel-Trénaunay syndrome (KTS) is a complex congenital anomaly, characterized by varicosities and venous malformations (VMs) of one or more limbs, port-wine stains, and soft tissue and bone hypertrophy. Venous drainage is frequently abnormal because of embryonic veins, agenesis, hypoplasia, valvular incompetence, or aneurysms of deep veins. We previously reported on the surgical management of KTS. In this article, we update our experience. Methods: Twenty patients with KTS underwent surgical treatment for VMs between July 1, 1987, and January 1, 2000. This group represented 6.9% of 290 patients with KTS who were seen at our institution during this 12.5-year study period. Surgical indications, venous anatomy (determined with duplex scan, contrast phlebography, magnetic resonance imaging or magnetic resonance phlebography), operative procedures, and complications were reviewed, and outcomes were recorded. Results: Twelve male and eight female patients (mean age, 23.4 years; range, 7.7-40.6 years) underwent 30 vascular surgical procedures in 21 lower limbs. All 20 patients (100%) had varicose veins or VMs, 13 (65%) had port-wine stains, and 18 (90%) had limb hypertrophy. Pain was the most common complaint, which was present in 16 patients (80%), followed by swelling in 15 (75%), bleeding in 8 (40%), and superficial thrombophlebitis and cellulitis in 3 (15%). Imaging confirmed patent deep veins in 18 patients, hypoplastic femoral vein in 1, and entrapped popliteal veins bilaterally in 1. Four patients (20%) had large persistent sciatic veins (PSVs). The CEAP clinical classification was C-3 for 17 patients (85%), C-4 for 1 patient (5%), and C-6 for 2 patients (10%). Stripping of large lateral veins, avulsion, and excision of varicosities or VMs were performed on all limbs. Three patients required staged resections. The release of entrapped popliteal veins was performed in both limbs of one patient; another underwent a popliteal-saphenous bypass graft. One patient underwent excision of a PSV. Open and endoscopic perforator vein ligation was performed in one patient each. Two patients (12%) had hematomas that required evacuation. No patients had caval filter placement; none had postoperative deep venous thrombosis or pulmonary embolus. The mean follow-up was 63.6 months (range, 0-138 months). All patients reported initial improvement, but some varicosities recurred in 10 patients (50%), an ulcer did not heal in one, and a new ulcer developed in one, 8 years after surgery. Three patients underwent reoperation for recurrent varicosities. Follow-up CEAP scores were C-2 in 10 patients (50%), C-3 in 6 patients (30%), C-4 and C-5 in 1 patient each (5%), and C-6 in 2 patients (10%). Clinical scores improved from 4.3 ± 2.2 to 3.1 ± 2.3. (P =.03). Conclusions: The management of patients with KTS continues to be primarily nonoperative, but those patients with patent deep veins can be considered for excision of symptomatic varicose veins and VMs. Although the recurrence rate is high, clinical improvement is significant, and reoperations can be performed if needed. Occasionally, deep vein reconstruction, excision of PSVs, or subfascial endoscopic perforator surgery is indicated. Because KTS is rare, patients should receive multidisciplinary care in qualified vascular centers. (J Vasc Surg 2000;32:840-7.)