Stenoses of the systemic venous pathways are a potentially dangerous complication after the Mustard operation. The acute and intermediate-term efficacy of balloon dilation of these stenoses has not previously been studied in a large group of patients. A retrospective analysis of clinical and angiographic data, with prospective clinical and echocardiographic follow-up, was performed in a consecutive group of 25 patients (17 male, 8 female) who underwent balloon dilation of the superior or inferior caval venous pathways. For 17 dilations of stenoses in the superior pathway, the mean pressure gradient decreased from 9.1±5.7 to 3.4±2.3 mm Hg (p<0.01), while the diameter of the stenosis increased from 5.9±2.9 to 11.2±3.0 mm (p<0.01). For 25 dilations of the inferior pathway, the mean gradient decreased from 4.3±1.8 to 1.4±1.1 mm Hg (p<0.01), while the diameter of the stenosis increased from 7.3±1.5 to 10.6±2.3 mm (p<0.01). Over a median follow-up of 3.5 years, 16 patients have been without symptoms or signs suggestive of recurrence of stenoses. In the remaining nine patients, 11 further procedures were performed at a median of 3.1 years after initial dilation. In five patients who had previously undergone dilation of the superior (3), inferior (1) or both (1) pathways, further dilations of the same pathway(s) and/or stent implantations were performed. Three patients, including one in whom superior caval venous stenosis had recurred, had developed a new stenosis of a previously undilated pathway, while in two patients no further dilations were required. Balloon dilation offers an alternative to reoperation for stenoses of the systemic venous pathways after the Mustard operation, and appears to provide satisfactory intermediate-term palliation. Recurrences of stenoses in previously dilated pathways, and new stenoses in previously unobstructed pathways, are commonly seen at follow-up. Alternative measures, such as placement of stents, need to be considered in the long-term management of these patients.