Increased diagnostic information may be derived with 99mTc diphosphonate from a detailed kinetic analysis of blood disappearance, urinary excretion and quantitative assessment of skeletal uptake. Blood and urine determinations were studied in 3 populations: normal volunteers, patients with negative bone scans and patients with positive bone scans. Quantitative imaging studies were performed in normal volunteers and patients with a scintillation camera interfaced to a computer. All subjects were scanned in the lower lumbar region up to 1 h after 99m diphosphonate administration. Blood levels exhibited a triexponential clearance pattern. Significant (P < 0.05) differences were observed for the 5 min blood and 0-1 h urine values among various groups. Computer-generated images showed an initial early uptake in bone, kidneys and soft tissue. Thereafter, a parallel fall-off in activity was observed in kidney and soft tissue, with a concomitant increase in bone. Skeletal uptake was different for normal and diseased bone.