We carried out a prospective study of the effectiveness of a diagnostic strategy in thirty consecutively seen patients who had skeletal metastasis. The diagnostic strategy consisted of the recording of a medical history, physical examination, routine laboratory analysis, plain radiography of the involved bone and chest, whole-body technetium-99m-phosphonate bone scintigraphy, abdominal ultrasound, computed tomography of the chest, abdomen and pelvis, fiberbronchoscopy and fibergastroscopy. After this evaluation, a biopsy of the most accessible osseous lesion was done in twenty four patients. On the basis of the our diagnostic strategy, we were able to identify the primary site of the malignant tumor in nineteen patients(63%). The laboratory values were non-specific in all patients. The history and physical examination revealed the occult primary site of the malignant tumor in one patient(3.3%) who had carcinoma of the breast. Plain radiographs of the chest established the diagnosis of carcinoma of the lung in three patients(9.9%). Computed tomography of the chest identified an additional three primary carcinoma of the lung(9.9%). Fiberbronchoscopy identified an additional one primary carcinoma of the lung(3.3%). Abdominal ultrasound established the diagnosis in three patients(9.9%). Computed tomography of the abdomen and pelvis established the diagnosis in four patients(13.2%). Fibergastroscopy established the diagnosis in two patients(6.6%). Examination of the biopsy tissue established the diagnosis in one patient(3.3%). So we recommend to perform plain radiographs of chest, abdominal ultrasound, chest C-T, abdomino-pelvic C-T, fiber-bronchoscopy, fibergastroscopy sequentially.