Activity levels of 99mTc-labeled compounds, 18F and 85Sr were obtained at 1, 3 and 5 h postinjection in normal and healing fractured bone and in soft-tissue rat specimens. Serial diagnostic bone images and blood and urine kinetics were obtained in patients with each of the Tc-labeled compounds. Computer-processed images were used to evaluate in vivo kinetics. 99mTc pyrophosphate provides the best overall characteristics for bone imaging. Improved quality and bioassay procedures are required before any 1 agent can be designated the radiopharmaceutical of choice for diagnostic bone imaging.