Introduction: We sought to establish a modern understanding of the safety and efficacy of trans-catheter pulmonary arterial angioplasty. Methods: A review of records in a sample of 104 dilations, out of a total of 711 procedures undertaken between January, 1996 and December, 2000, provided descriptive information regarding technique, adverse events, and changes achieved in luminal diameter. Because evidence during the review of angiograms suggested substantial differences according to whether the stenotic lesions were positioned proximally or distally within the pulmonary arterial tree, all analyses incorporated this classification. Results: We reviewed stenoses in 203 pulmonary arteries, 38% located proximally and 62% distally, with follow-up available concerning dilation in 92 vessels. Proximal dilations frequently involved a prior surgical site, and appeared more compliant and amenable to conventional angioplasty, as evidenced by more common elimination of the waist, but also more recoil, then requiring placement of stents. In contrast, distal lesions frequently required balloons capable of sustaining high pressures of inflation, and larger balloons relative to the size of the vessels. The proportional increase in diameter was greater for distal sites, at 90 plus or minus 77%, compared to proximal, at 64 plus or minus 70%, p equal to 0.002. Serious adverse events occurred in 3 of 104 procedures, giving a rate of serious adverse events of 2.9%. At follow-up, 9 of 92 vessels (10%), 95% confidence intervals from 5% to 18%, returned to their diameters prior to dilation, with no difference in the rate of restenosis according to the site of dilation. Conclusion: Our findings indicate the need to distinguish, and to consider, the important differences in technical issues and outcomes, when performing dilations at proximal as opposed to distal sites. Although angioplasty is effective therapy for pulmonary arterial stenosis, a subset of vessels, more often distal, remain resistant to conventional techniques.