A rational analysis procedure for solitary lesions on whole bone scan-ning was offered. This study was undertaken to analyze retrospectively solitary le-sions which obtained final diagnose through the following aspects: (1) diagnosis ofbone metastasis, (2) the incidence of bone metastasis in different tumor, (3) the mostpossible lesion sites indicating bone metastasis, (4) morphological analysis of solitarylesions. The results are: (1) The incidence of solitary lesions in 2465 cases on wholebone scanning is 15.3%. (2) The rate of bone metastasis is 24.8% in 282 patientswith primary malignancy. The rate of bone metastasis is 6.3% in 64 patients withoutprimary malignancy, and the total diagnostic rate of bone metastasis is 21.4% in 346patients. (3) In patients with primary malignancy, the incidence of bone metastasis ofsolitary lesions is as follows respectively: bronchi cancer 36.1%(22/61); breast cancer23.8%(20/84); prostate gland 17.2%(5/29); other urinary system cancer 22.2%(4/18):G.I. system cancer 16.9%(10/59); others 29.0%(9/31). There is no significant differ-ence in different cancer. (4) In patients without primary malignancy, 93.7%(60/64) ofsolitary lesions are benign. (5) From anatomical point of view, we found the diagnos-tic rate of bone metastasis is as follow: 30% in spine; 34.2% in pelvis; 36.4% in skull;10.8% in other bones. There are significant differences in four groups. It is concludedthat: (1) The diagnostic rate of bone metastasis in solitary lesions is 21.4%. (2) Themost possible solitary lesions indicating osseous tumor spread are at spine, pelvic andskull. (3) Special attention to "cold" and streak like lesions should be paid. (4) Aclinical analysis procedure for diagnosis of solitary lesions has been summarized outhere.``