Lung cancer is common in people, representing the leading cause of death in men and women over 35 years of age. In humans lung cancer is strongly linked to smoking. By contrast, most lung tumors in dogs represent spread of cancer from elsewhere in the body and primary lung cancer is rare in dogs. It is most common in older dogs; signs include coughing, exercise intolerance and, rarely, difficulty breathing or lameness with swollen legs due to a syndrome associated with the lung cancer called hypertrophic osteopathy. Often, dogs show no signs of their cancer and a lung mass is identified on chest x-rays taken for non-related reasons. Lung cancer is strongly suspected when x-rays show a circular mass in the lungs. A CT scan helps to check for spread of the tumor to other lung lobes and lymph nodes. If the tumor has not spread to lymph nodes or other lung tissue, surgery is recommended. The average survival after surgery is about 1 year, with some dogs living much longer or even cured. For dogs with biopsies that suggest more aggressive types of lung tumors, incompletely removed tumors, or spread of lung cancer treatment with chemotherapy is recommended. The CCOGC is collecting blood samples as well as normal and cancerous lung tissue samples from dogs with naturally occurring lung cancer with the goal of furthering research efforts against this disease.