A simple and inexpensive method for the estimation of stannous ion, Sn (II), in radiopharmaceutical kits is described. The method used is a potentiometric titration of Sn (II) in 1 N HCI medium, using potassium iodate as the oxidizing agent in an atmosphere of nitrogen. The apparatus includes pH meter, a platinum electrode, and a simple titration cell. Several commonly used radiopharmaceutical kits were analyzed for their Sn (II) content using this method. These studies indicate that the procedure can be used, as a routine quantitative test for the Sn (II) content of various 99mTc-labeled radiopharmaceuticals.