Abstract: This paper reports the polarographic behavior of the complex of Y³⁺ with basic dye rhodamine B.Near-1.5V (SCE) rhodamine Bhas a large adsorptive single sweep polarographic wave in the presence of ammonium chloride and diphenylg-uanidine. Y³⁺ decreases the height of this derivative wave. Under the optimum conditions, such as 0.4.Mammonium chloride, 8.0×10^-5 Mrhodamine B, 1.0×10^-4 Mdiphenylguanidine, pH 4.5-5.0, there is a linear relationship between 1× 10^-7-l×10^-6M Y²⁺ and the decrease of the wave heights. Heavy rare earth elements behave similarly as Y³⁺ , thus the total amount of them may be determined.The mechanism of this system has been studied by means of dc, dpp, single sweep normal and derivative polarographys. The results indicated that Y³⁺ may form an ion-association complex with rhodamine Band diphenylguanidine as shown in the following.