Radioisotope bone scanning is frequently used as the major, and sometimes the only, diagnostic test for neoplasia in bone. While the evidence is convincing that bone scans are frequently more sensitive than roentgenographic bone surveys for detection of metastatic bone disease, there are false-negative results for a variety of reasons, and positive findings must be interpreted with caution. Scans also appear more limited than roentgenograms in their usefulness for evaluating changes in abnormal bone structure. Case histories and discussion are offered to indicate that usually both radioisotope bone scans and roentgenographic bone surveys should be obtained for initial screening and subsequent assessment of bone metastases.