A 70-yr-old man who was diagnosed as early gastric cancer showed leukocytopenia after total gastrectomy. Osteosclerotic findings on radiography were not remarkable. 99mTc-HMDP bone scintigraphy showed diffusely increased uptake in the axial skeleton, but visualization of the kidney and urinary bladder was apparent. However, whole body 201Tl-chloride scintigraphy showed diffuse abnormal visualization of axial skeleton. Physical and ultrasonographic examination indicated no abnormality in prostate. Afterward, further investigation, including bone marrow biopsy and immunohistochemical study, confirmed the diagnosis of bone metastasis from prostatic cancer. Microscopically, metastatic tumor cells were located in the intertrabecular space. Furthermore, no osteoclastic bone resorption or new trabecular bone formation was seen in this biopsy specimen. These findings suggest that whole body 201Tl-chloride scintigraphy can be a useful non-invasive diagnostic tool to investigate patients with suspicious malignancy in the bone marrow.