Three new samples of stannic molybdate with Sn:Mo ratio of 2:1 have been synthesized by mixing 0·1M-SnCl₄ and 0·1M-Na₂MoO₄ solutions in the volume ratios 2:1 (sample 1), 4:3, and 1:1 at pH 1. They are amorphous, monofunctional ion exchangers with an ion exchange capacity of ca. 0·54–0·73 mequiv g^–1. The K_d values of 25 cations have been determined on these samples in aqueous medium. Sample 1 was found to be the most stable and K_d values on this sample were determined at pH 1,2,3, and 4. The selectivity of metal ions was also tested on this sample in the presence of 0·01–0·5M-ammonium chloride. The analytical importance of these samples has been established by some useful separations.