Vascular complications are the major cause of morbidity and mortality after liver transplantation, particularly in pediatric patients, owing to their smaller vascular diameters. Between September 2001 and June 2004, among 21 (16 boys and 5 girls) pediatric liver transplantations of mean age 8.3 +/- 5.1 years, hepatic arterial thrombosis (HAT) was diagnosed in 2 (9.5%) patients, and hepatic arterial stenosis (HAS) in 4 (19.4%). Vascular patency was evaluated with Doppler ultrasonography every 12 hours in the first postoperative week and daily in the second postoperative week. When occlusion was suspected, conventional angiography was performed. Thrombectomy was performed in one patient, and thrombectomy and reanastomosis were performed in another patient with HAT. Two patients with HAS were treated with balloon angioplasty. A third patient was treated with balloon angioplasty and endoluminal stent placement at the same time. The last patient with HAS had an intimate dissection, which occurred 24 hours after balloon angioplasty, that was treated with subsequent endoluminal stent placement. Mean follow-up for the patients with vascular complications was 9.5 +/- 5.7 months (range, 4 to 18 months). The overall mortality rate was 14.1% (3/21); however, no deaths were caused by vascular complication. Routine Doppler ultrasonographic evaluation is an effective choice for diagnosing vascular complications seen after liver transplantation. Immediate surgical intervention is required for acute vascular complications, whereas late complications may be treated with balloon angioplasty and/or endoluminal stent placement.