Thorium-229 can be used to produce Bi-213. Researchers in phase I human trials are investigating the use of antibodies labeled with Bi-213 for selectively destroying leukemia cells. Other types of cancer may potentially be treated using similar approaches. Crude Th-229 was liberated from Rachig rings by sonication in 7.5 M HNO3 followed by filtration. Contaminants included significant levels of uranium, a number of other metals, and radiolytic by-products of di-(2-butyl) phosphoric acid extractant (which was used in the original separation of U-233 from thorium). Thorium was selectively retained on Reillex HPQ anion-exchange resin from 7.5 MHNO3 at 65 degrees C, where U(VI), Ac(III), Fe(III), Al(III), Ra(II), and Pb(II) were eluted. Thorium and uranium isotherms on Reillex HPQ are reported. The thorium was then easily eluted from the bed with 0.1 M HNO3. To overcome mass transfer limitations of the resin, the separation was conducted at 65 degrees C. The resin stood up well to use over several campaigns. Other researchers have reported that HPQ has excellent radiological and chemical stability. The eluted thorium was further purified by hydroxide precipitation from the organic contaminants. This process yielded 65 mCi of Th-229.