The skeletal neoplasms of small dogs are characterized poorly. In this retrospective study, the bone tumors of 37 small dogs (with body weights less than 15 kg), 74 large dogs (with body weights greater than 25 kg), and 134 small dogs previously reported in the literature were compared. Metastases accounted for about 25% of the bone tumors in small dogs, but less than 5% of the bone tumors in large dogs. In small dogs, osteosarcomas represented less than 50% of all skeletal neoplasms, frequently affected the axial skeleton, and had no apparent predilection for the distal radius. In this series and in the literature, fewer than 10 small dogs with appendicular osteosarcoma were treated with curative intent. Clinicians should use caution when extrapolating information on the biological behavior of osteosarcoma from large- and giant-breed dogs to small dogs.