BACKGROUND Endovascular therapy for symptomatic atherosclerotic renal artery stenosis (ARAS) is considered effective. This study evaluates the factors that impact long term anatomic and functional outcomes of endovascular therapy of ARAS in patients with a solitary functioning kidney. METHODS We performed a retrospective analysis of records from patients who underwent endovascular intervention for ARAS and identified patients with a solitary functioning kidney (absent or nonfunctioning contralateral kidney) and patients with contralateral normal kidney (for comparison) between January 1990 and January 2008. Indications for intervention in the solitary functioning kidney were poorly controlled hypertension (diastolic blood pressure [BP] >90 mm Hg on >3 antihypertensive medications) and/or elevated creatinine (Cr >/=1.5 mg/dL). Clinical benefit was defined as freedom from composite recurrent symptoms (recurrent hypertension or renal-related morbidity-increase in persistent creatinine >20% of baseline, progression to hemodialysis, and death from renal-related causes), anatomic patency and patient survival were measured. RESULTS A total of 242 patients (56% male, average age 69 years, range, 45-90) underwent angioplasty (23%) or primary stenting (77%) of a single renal artery with a normal contralateral renal vessel and kidney and 73 patients (58% male, average age 70 years, range, 52-89) underwent angioplasty (37%) or primary stenting (63%) for a solitary functioning kidney. There were no significant differences in mortality or morbidity between the groups. There was a significant difference in the long-term survival with 55 +/- 8% patients with a normal contralateral kidney vs 27 +/- 7% patients with a solitary functioning kidney alive at 10 years. Clinical benefit was 67 +/- 6% and 67 +/- 4% at 5 years and 63 +/- 8% and 62 +/- 4% at 10 years for solitary functioning kidney and normal contralateral groups, respectively. Using proportional hazard analysis, the predictors of long-term clinical benefit were ipsilateral kidney size (>9 cm), no immediate deterioration in function, and an estimated Glomerular Filtration Rate (eGFR) >30 mL/min/1.73m(2). Neither control of diabetes nor the administration of statins was shown to influence outcomes in the solitary functioning kidney. CONCLUSIONS Intervention in patients with a solitary functioning kidney is a safe procedure and improves or stabilizes renal function in 82% of patients. Clinical benefit is dictated by preoperative GFR, renal size, and the occurrence of acute functional injury after the procedure.