Tin is an essential ingredient of most technetium-99m radiopharmaceuticals but its in-vivo distribution and long-term fate are not well understood. This work describes distribution in mice of several tin-117m labeled compounds. The results indicate that stannic-HEDTMP appears to be the best overall bone localizing agent with very low blood, muscle, kidney, or liver uptake, and its binding to bone is higher than that of tin-117m-DTPA, which make it potentially useful as an agent for skeletal scintigraphy and radiotherapy of bone tumors. Tin is an essential ingredient of most technetium-99m radiopharmaceuticals but its in-vivo distribution and long-term fate are not well understood. This work describes distribution in mice of several tin-117m labeled compounds. The results indicate that stannic-HEDTMP appears to be the best overall bone localizing agent with very low blood, muscle, kidney, or liver uptake, and its binding to bone is higher than that of tin-117m-DTPA, which make it potentially useful as an agent for skeletal scintigraphy and radiotherapy of bone tumors.