Fifty-four dogs with primary tumors of the rib were evaluated. Thirty-four dogs had osteosarcomas, 15 dogs had chondrosarcomas, three dogs had hemangiosarcomas, and two dogs had fibrosarcomas. Forty-nine dogs had en bloc excision. Within the osteosarcoma group, nine animals received postoperative adjuvant chemotherapy. These animals had significantly longer median disease-free intervals (225 days) and median survival times (240 days) than dogs with osteosarcoma treated by surgery alone (median disease-free interval, 60 days; median survival, 90 days). Chondrosarcoma had a better prognosis (median disease-free interval, 1,080 days; median survival, 1,080 days) than osteosarcoma, hemangiosarcoma, or fibrosarcoma of the rib. Age, weight, sex, number of ribs resected, tumor volume, and total cisplatin dose did not influence survival nor disease-free interval.