We report on 5 patients with renal artery stenosis after renal transplantation. Renal arteriography showed the stenosis to be localized at the line of arterial anastomosis. The patients presented with refractory hypertension, with or without renal failure, 10 days to 13 months after transplantation. Percutaneous transluminal balloon angioplasty in 4 patients failed in 3 and produced temporary improvement in 1. Resection of the stenosis resulted in dramatic improvement of the clinical state in all 5 patients. Histological examination of the resected stenotic segment revealed a nodular fibrotic lesion at the anastomotic line in all cases, and was associated with extensive calcification in 3. Anastomotic line stenosis should be recognized as a specific entity causing transplant renal artery stenosis. The pathological changes observed explain the failure of transluminal angioplasty and suggest that surgical repair is the treatment of choice. Possible factors in the etiology of anastomotic line stenosis are discussed.