The occurrence of soft-tissue tumors in beagles given 90Sr (88 dogs), 228Ra (76 dogs), or 228Th (81 dogs) as young adults and followed throughout their lifespans was compared with that of 133 control beagles given no radioactivity. For animals injected with 228Ra, tumors of the eye were more prominent (p < 0.05) than in the controls, and soft-tissue tumors of cavities in the head (excluding the brain, mouth, and eye) were more prominent in dogs given 90Sr than in the controls (p < 0.05). There was some indication that eye tumors in animals given about 0.56 kBq 228Th kg-1 were associated with their radionuclide exposure. For tumors at a few other locations, the relative occurrence was greater (p < 0.05) in the controls. These included malignant tumors of the testis and malignant plus benign tumors of the mammae and vagina in 228Th dogs; both malignant and malignant plus benign tumors of the mouth and testis, and malignant plus benign tumors of the mammae and vagina in 228Ra dogs; and malignant plus benign tumors of the mammae in 90Sr dogs (p > 0.05 by Odds Ratio Chi Square analysis but p < 0.05 by Fisher's Exact Test). Differences in relative occurrence between radioactive dogs and controls of all other tumor types that appeared in any of the animals (notably lymphosarcoma, lymph node tumors, leukemia, mast cell tumors, liver tumors, etc.) were not statistically significant (p > 0.05). Intercurrent mortality, mainly from bone cancer, was higher in the radioactive dogs than in the controls. Mean survival was reduced in the dogs given 90Sr, 228Ra, or 228Th (13.17 +/- 2.64 y in controls, 10.95 +/- 4.06 y in 90Sr dogs, 9.07 +/- 3.61 y in 228Ra dogs, and 9.20 +/- 4.15 y in 228Th dogs). Attenuated lifespans could account, at least in part, for the relative paucity of soft-tissue tumors not induced by radiation among the groups of dogs given radioactivity and occurring near the end of life for control animals.