Glassy, nanocrystaline antimony-doped hydrous tin dioxide was alkali precipitated from acidic metal chloride solution. The material has good thermal stability and granular physical form that enables its use in a conventional column. The material shows excellent, almost quantitative, uptake properties for 99Tc radionuclide. Its distribution coefficients (Kd values) for 99Tc were typically over 1 000 000 (ml/g) in solutions of one molar ionic competition (at neutral pH) and the uptake remained high over a broad pH range (2-112, 3, 4, 5, 6, 7, 8, 9, 10, 11). By comparison, conventional cation/anion resins yielded Kd values of less than 200. The Tc uptake mechanism of antimony-doped tin dioxide is most likely a sorption process that cannot be categorized as typical cation or anion exchange. Redox reactions between Tc and Sb were speculated as being the phenomenon. Thermal treatment increased the materials crystal size from amorphous to 15nm and changes in the oxidation state of antimony from +3 to +5 occurred at temperatures above 400 degrees C. Also, the material's Tc uptake properties were increased by the thermal treatment.