The kinetics and imaging characteristics of 99mTc-labeled stannous pyrophosphate were evaluated in 30 patients. Blood chemistries, urinalyses, serial blood activity measurements and 24-hour fractionated urine activity assays were obtained in selected patient studies. Digital gamma camera images were recorded on magnetic disk and quantitatively analyzed. Total body rectilinear scans were also recorded. Results indicate that 99mTc pyrophosphate is useful for bone imaging. Preparations yielded reproducibly high binding efficiencies; soft tissue clearance was rapid; no pharmacologic effects were observed; and count levels and contrast between lesion-involved bone and normal bone were adequate. Image quality was acceptable between 1 and 6 hours after administration. Abnormal areas were detected at all imaging times; however, the best image quality was usually observed in the delayed views.