A total of 2530 consecutive bone scans were examined to evaluate the number and the type of soft tissue neoplasms detected with bone-seeking phosphonates. Sixty-eight primary or secondary soft tissue neoplasms of 63 patients accumulated 99mTc -methylene diphosphonate and 2 accumulated 99mTc -diphosphonate, and one metastasis was seen as a nonactive 'cold' focus in the urinary bladder. The localization of tumors was: 19 in the lung, 15 in the liver, 11 in the kidney, 10 in the peritoneal cavity or ascites, 5 in the large bowel, 4 in the vascular or lymphatic system, 3 in the connective tissue or muscles, 2 in the ovary, 1 in the urinary bladder, and 1 in the brain. Our results differ in many respects from those reported in the literature. The causes of the differences are discussed.