The extraction of (\mathrm{Y}^{3+}) from (\mathrm{Sr}^{2+}) has been carried out with a new type of extractant, sym-dibenzo-16-crown-5-oxyacetic acid, in chloroform using ({ }^{87 \mathrm{~m}} \mathrm{Sr}) and ({ }^{90 \mathrm{~m}} \mathrm{Y}) as tracers. The extraction efficiency of (\mathrm{Y}^{3+}) depends strongly on the (\mathrm{pH}) of aqueous phase, whereas the extraction of (\mathrm{Sr}^{2+}) is negligible at (\mathrm{pH}<6.5). The dependence of the concentration of sym-dibenzo-16-crown-5-oxyacetic acid on the distribution ratio of (\mathrm{Y}^{3+}) is linear and has a slope of about 2. This suggests that (\mathrm{Y}^{3+}) appears to form a (1: 2) complex with ligand. The new method for preparing highly purified ({ }^{90} \mathrm{Y}) by solvent extraction from equilibrium ({ }^{90} \mathrm{Sr}^{90}{ }^{90} \mathrm{Y}) has been developed. The radionuclide purity of ({ }^{90} \mathrm{Y}) obtained is estimated to be (10^{-8}) and the recovery rate of ({ }^{% /} \mathrm{Y}) is about (99 %). & 1995 Academic Press. Inc.