Polyamine (PA) accumulation has been associated with blood-brain barrier (BBB) disruption and vasogenic oedema after cold injury. PAs and water content were measured in a rat spinal cord model of late-delayed radiation injury and were found to be elevated at paralysis. The elevated PA levels could be significantly reduced by treatment with difluoromethylornithine (DFMO). In unirradiated rats DFMO reduced putrescine to undetectable levels after 10-12 weeks. These data suggest that blockade of PA synthesis may be useful in treating the vasogenic oedema of radiation injury and may improve CNS radiation tolerance.