To compare 99mTc-polyphosphate and 18F for use in orthopedics, 79 patients were examined with both. Fifty cases were suitable for analysis. While the extraskeletal uptake of 18F was found to be negligible, 99mTc-polyphosphate may accumulate considerably in pathologic soft tissue, e.g., in soft-tissue tumors and in inflamed synovial tissue. This soft-tissue Tc accumulation may obscure the osseus uptake, notably in the examination of joint regions, commonly the regions of interest in orthopedics. After simultaneous administration of both agents, quantitative measurements were performed on specimens of bone and synovial tissue from diseased joints in human patients and in rabbits. The uptake of 99mTc-polyphosphate in synovial tissue was shown to be about seven times that of 18F, while their uptakes in bone were equal. In short, 99mTc-polyphosphate, a valuable tracer in general, is hardly the agent of choice in orthopedics.