A folate-receptor-targeting radiopharmaceutical, Ga(III)-deferoxamine-folate (Ga-DF-Folate), was radiolabeled with two positron-emitting isotopes of gallium, cyclotron-produced 66Ga (9.5 hour half-life) and generator-produced 68Ga (68 minute half-life). The [66Ga]Ga-DF-Folate was administered to athymic mice with folate-receptor-positive human KB cell tumor xenografts to demonstrate that microPET mouse tumor imaging is feasible with 66Ga, despite the relatively high positron energy of this radionuclide. Using the athymic mouse KB tumor xenograft model, dual-isotope autoradiography was also performed following i.v. co-administration of [18F]-FDG, a marker of regional metabolic activity, and folate-receptor-targeted [ 111In]In-DTPA-Folate. The autoradiographic images of 1 mm tumor sections demonstrate the gross heterogeneity of the KB cell tumor xenograft, as well as subtle disparity in the regional accumulation of the two radiotracers.