Objective: Bone metastases are a major problem in several tumor entities (e.g., mammary or prostate carcinomas) affecting the therapeutic procedure or the patient's prognosis. SPECT or PET are promising techniques not only to identify bone tumors but also to use therapeutic radionuclids (e.g., ¹⁵³Sm) for localized irradiation. For the development of new tracer compounds which specifically accumulate in bone metastases experimental animal models of bone metastases are needed. Methods: In order to obtain a tumor cell spread comparable to that leading to hematogenic bone metastases a surgical procedure for tumor cell injection into the hind limb of Sprague-Dawley rats was developed. As a tumor model the Walker carcinoma 256 was used which is known to form bone metastases. For tumor implantation the Arteria epigastrica caudalis superficialis (a branch of the femoral artery) was canulated and approx. 10⁵ cells were injected. Afterward the artery was ligated. For visualizing of the tumor growth positron emission tomography (PET) with ¹⁸F-fluoride was performed weekly on a m-PET system. After three to four weeks tumor histology was determined. Results: Two weeks after tumor cell inoculation PET images showed first signs of bone metastases in approximately 70% of the animals. The tumors were located either in the proximal tibia/fibula or in the distal femur. At this time the animals showed no restrictions in mobility. The tumors grew constantly over time. The final histological analysis showed a tumor invasively growing into the bone matrix. Conclusion: With this model of bone metastases it becomes possible to test whether new tracers for SPECT or PET imaging show in vivo a high specific uptake in bone metastases and therefore are suitable for diagnosis and image-based dosimetry and consequently to develop new compounds for radiotherapy.