Hypoxia in tumours has been associated with an increased resistance to radiation and chemotherapy, and increased metastatic potential. Hypoxia-inducible factor 1-alpha (HIF-1alpha) is a transcription factor induced by hypoxia. Glucose transporter 1 (GLUT-1), a downstream product of HIF-1alpha pathway activation, is over-expressed in a variety of human tumours. The purpose of this study was to determine if GLUT-1 is expressed in canine osteosarcomas (OSAs) and if the expression is related to tumour necrosis and outcome. Immunohistochemistry was performed on 44 histologically confirmed OSA tissue samples to assess expression of GLUT-1. Of 44 cases, 27 (61%) expressed GLUT-1. There was no statistical correlation between GLUT-1 and disease-free interval, survival time or percentage of necrosis. As hypothesized, GLUT-1 is present in canine appendicular OSAs. A more objective evaluation of GLUT-1 and other proteins in the HIF-1alpha pathway may be warranted.