Tumor hypoxia is an important mediator of radiation therapy resistance. We conducted a study to investigate whether an oxygen therapeutic based upon DDFPe could increase tumor oxygen tension in hypoxic tumors and improve radiation response. The material shows promise as a radiation sensitizer. Single bolus doses of 0.6 cc/kg (2% w/vol DDFP) resulted in tumor pO2 increases up to 400% lasting up to 2 hours and significantly improved survival of radiated animals. DDFPe requires a much lower dose of fluorocarbon for use as an oxygen therapeutic.