Four cases of hypertrophic osteopathy (HO) associated with pulmonary metastasis were diagnosed in years 2007 and 2008 at the veterinary hospital of UNIP (Campinas Campus). An undetermined age mixed breed male dog (patient I), a 7 year old female Boxer (patient II), a 5 year old female mixed breed (patient III) and a 6 years old female Saint Bernard (patient IV) presented with history of lethargy, weight loss, hyporexia, dyspnea, panting, reluctance to move and swollen limbs. On physical examination all patients were in poor body condition, had swollen, warm and painful limbs. Thorax radiographs showed pulmonary metastasis. Limbs' radiographs showed periosteal proliferation. Patient I also had a firm mass on the thorax. Although HO was diagnosed, the primary tumor was not identified; owner did not authorize any further diagnostic tests. Patient II also had a mammary tumor. Owner decided for euthanasia due to the lack of a better prognosis. Patient III had history of mammary chondrosarcoma and mastectomy 9 months previous. Due to the poor clinical condition owner decided for euthanasia. Patient IV had history of osteosarcoma which was treated with amputation of the right forelimb and four rounds of chemotherapy with carboplatin 4 months previous. Symptomatic treatment for pain was given. The patient returned clinically worse and euthanasia was indicated. HO is a syndrome characterized by periosteal proliferation along the shafts of long bones secondary to malignant and non malignant diseases within the thorax and more rarely the abdomen. HO is commonly reported as a paraneoplastic syndrome due to primary and metastatic lung tumors, but it is also reported with tumors without thorax involvement. Nonneoplastic conditions such as pneumonia and heart worm disease can also cause HO. The pathogenesis is unknown, however it is thought that HO develops as a result of neurologic stimulation and an increase of periosteal blood flow with subsequent overgrowth of connective tissue and periosteal proliferation. Patients with HO presents with lameness, reluctance to move, painful, swollen, firm and warm limbs. If the underlying primary disease is treated, HO resolves. Treatment of pain and discomfort must be done symptomatically. The diagnoses of all cases were made according to the clinical signs in adjunction with evidence of pulmonary metastasis and periosteal proliferation in long bones. Treatment of the HO cases reported was difficult to install due to the presence of diffuse pulmonary metastasis and subsequent poor prognosis and reluctance of the owners in treating them.