Radiopharmaceuticals are applied in nuclear medicine for therapy and diagnosis of disease and organ function. The radiopharmaceuticals can enter the human body as radioisotopes alone or radioisotopes connected to different chemical compounds. Some radiopharmaceuticals are used for renal function and anatomy. The radiopharmaceuticals for investigation of renal function and structure can be divided into three categories: first, the radiopharmaceuticals filtered by the glomerulus, second, the radiopharmaceuticals retained in the renal tubules via proximal tubule receptor-mediated endocytosis from the glomerular filtrate, and third, the radiopharmaceuticals primarily secreted by the renal tubules via the organic anion transporter. 131I-Hippuran and 99mTc-MAG3 are two important radiopharmaceuticals in renal scintigraphy. 99mTc-MAG3 is a renal tubular agent which was introduced in 1986 as an alternative for the use of 131I-Hippuran with similar pharmacokinetic and human renogram pattern. 99mTc-MAG3 is highly protein-bound and is removed from the plasma primarily by the organic anion transporter 1. 99mTc-MAG3 is used more than 99mTc-DTPA for patients with suspected obstruction and impaired renal function (IRF) and is applied in almost 70% of the renal scans performed in the US.