The effect of NH4NO3on the expression of take-all in wheat and on the ability of fluorescent pseudomonad bacteria to decrease the growth of the pathogen and the symptoms of the disease was examined in a nitrogen-deficient acidic soil from Western Australia. Application of NH4NO3increased the fresh weight of shoots, decreased root weight and length, and offset some of the deleterious effects of infection. Inoculation withGaeumannomyces graminisvar.tricitireduced shoot weight and root weight and length at all but the highest level of applied nitrogen. Fluorescent pseudomonads applied to wheat seed (at approximately 108colony-forming units/seed) reduced seed germination and failed to reduce the severity of take-all expressed as weight or length of shoots or N content. Although the density of black runner hyphae ofG.graminisvar.tricitiwas reduced at 40 days and the proportion of root colonized by the pathogen was lower at 28 days with bacterization under severe nitrogen deficiency, no effect of the bacteria was observed if N was added.Key words:Gaeumannomyces graminisvar.triciti, fluorescent pseudomonads, wheat, nitrogen.