We have studied the relative carcinogenicity of polonium-210 (210Po) administered intratracheally in Syrian hamsters by two different methods. In the first, 210Po was instilled in soluble form in a saline solution yielding a uniform distribution of radioactivity throughout the lung parenchyma. In the second, 210Po was administered adsorbed onto Fe2O3 carrier particles that yielded a highly non-uniform distribution of radiation dose. With lifetime doses averaged over the whole lungs of 55–2700 rad, the tumor yields for the non-uniform “hot-spot” irradiation were equal to or less than those for uniform exposure. This finding supports the conclusion that the assessment of the hazards of inhaled alpha emitters utilizing a model based on uniform distribution is a reasonable approach for radiation protection purposes.