Abstract: The preparation and in vivo biodistribution in m ice of several 117 Sn m labelled compounds are studied. The results indicate that the favourable half-life and decay characteristics of 117 Sn m in various stannic compounds, especially stannic-TTHMP. It appears to be the best overall bone localizing agent with very low blood, muscle, kidney, or liver uptake and the binding of 117 Sn m-TTHMP to bone is higher than that of 117 Sn m-DTPA. This makes it potentially useful as an agent for skeletal scintigraphy and radiotherapy of bone tumors.