Tc-99m pertechnetate scintigraphy was compared with Tl-201 chloride and Ga-67 citrate to evaluate the avidity of Tc-99m pertechtate for malignant soft-tissue tumors. Twenty-three patients with malignant soft-tissue tumors underwent scintigraphic studies. All 23 received Tc-99m and Tl-201, whereas 14 also were injected with Ga-67. In 21 (91%) of the 23 patients, Tc-99m accumulated extensively in the tumors. Tl-201 accumulated in 12 (52%) of the 23 tumors. Ga-67 accumulated in only 5 (36%) of the 14 tumors. The avidity of Tc-99m for myxoid tumors was markedly different from the other two agents. Tc-99m accumulated in all eight myxoid tumors, while neither Tl-201 or Ga-67 showed marked accumulation except for one patient with increased accumulation of Tl-201. This study shows that Tc-99m pertechnetate has the potential to localize malignant soft-tissue tumors and may be useful in the evaluation of these tumors.