Summary Western gall rust, caused by Peridermium harknessii J. P. Moore, causes severe disease on nearly all species of hard pines including Pinus radiata, and presents a potential threat to the softwood industry of Australia and New Zealand should the pathogen be accidentally introduced into these countries. The pathogen causes formation of stem galls, which kill young trees and result in stem defect in older trees. In several regions of Australia where P. radiata is the main softwood species, it is likely that environmental conditions may be suitable for outbreaks of disease epidemics. There is some evidence that variation in resistance to western gall rust occurs both within and between native populations of P. radiata. In the event of introduction of P. harknessii into Australia the future of radiata pine may depend on the utilisation of genetically controlled resistance, mature plant resistance and suitable management practices.