Use of iodinated contrast for vascular imaging can be associated with nephrotoxicity and hypersensitivity reactions. Renal injury following conventional angiography is more likely to manifest in the setting of preexisting renal dysfunction. In the setting of suboptimal renal allograft function, these considerations are particularly relevant. Recently, CO2 has received attention as a nontoxic, injectable, rapidly absorbed gas that is a cost-effective alternative to standard contrast agents in high-risk patients, such as renal transplant recipients. We report the clinical course of a patient with transplant renal artery stenosis and a serum creatinine of 2.8 mg/dl who has successfully undergone angiography and percutaneous transluminal angioplasty using CO2 as the sole contrast agent. This case illustrates the potential use for CO2 as a contrast agent for vascular imaging in patients with suboptimal renal function who require definitive vascular imaging or therapy.