Eriochrome cyanine R (ECR) is investigated as a collector for separation and flotation of hafnium from zirconium through the use of an oleic acid surfactant. Selective separation of Zr(IV) is achieved at pH 2 with maximum efficiency, whereas Hf(IV) is completely separated at pH 7.0-7.5. Excess ECR is used to avoid interferences from foreign ions without any effect on the separation efficiency. The procedure is successfully applied to the determination of Zr(IV) and Hf(IV) in real samples. A flotation mechanism is proposed.