Significant isotopic fractionation of gallium has been observed during elution through an anion-exchange resin in the thio-cyanate form. Two samples of NBS Standard Reference Material 994 (certified 69Ga/71Ga = 1.50676 [plus or minus] 0.00039) were passed through the ion-exchange columns, and fractions were analyzed for isotopic composition and gallium contend by using thermal ionization isotope dilution mass spectrometry. The results show a depletion of the light isotope in early fractions from the columns, with a steady increase in the light isotope throughout the elution. A materials balance of the product of the isotopic composition and gallium content of each fraction is in agreement with the isotopic composition of the starting material.