Patients with diffusely increased uptake in both kidneys (often referred to as "host kidneys") on Tc-99m-MDP bone imaging were evaluated. Among 2056 patients reviewed, this finding was seen in 13 patients (0.63%): four with liver cirrhosis, two with lung cancer, one each with primary hepatoma, Hodgkin's disease, malignant lymphoma, thyroid cancer, leukemia, sideroblastic anemia and diabetes mellitus. Renal vascular disease and iron overload are considered to be the major causes of this finding.