An analysis was made of 17 cases of microscopically proven rib neoplasms, with the objective of evaluating the variability of clinical and radiographic findings, the neoplastic cell types, the occurrence of metastases, and the survival time following the diagnosis. In 15 dogs with primary rib neoplasms and in 2 dogs with secondary (presumably metastatic) rib neoplasms, the clinical signs commonly included dyspnea and a localized swelling on the thoracic wall. For the dogs with primary rib neoplasms, the mean age was 4.5 years, with a range of 1.3 to 16 years. On radiography, rib osteolysis, extra and/or intrathoracic soft tissue masses often containing areas of mineralization, and pleural effusion were commonly identified. Ribs 5 through 9 were the most commonly affected and the right side was involved twice as often as the left side. Osteosarcoma was the most frequently diagnosed tumor, but chondrosarcomas and hemangiosarcoma were also found. At necropsy, over 50% of the dogs with primary rib neoplasms had metastases in the lungs. Less than 10% of the dogs with primary rib osteosarcomas survived more than 4 months after the diagnosis.