The interaction between several species of arbuscular mycorrhizal fungi, micropropagated strawberry plants and Phytophthora fragariae, the pathogen that causes red stele disease of strawberry plants, was investigated. The optimum temperature for germination of zoospore cysts of P. fragariae in vitro was found to be 15°C, and growth of the emerging germ tube was significantly orientated towards the strawberry root tip. Cyst germination was reduced in the presence of a mycorrhizal strawberry root. Elsanta was more susceptible to P. fragariae than the cultivar Rhapsody. A low level of colonisation of Elsanta with the arbuscular mycorrhizal fungi Glomus mosseae, Glomus intraradices or Glomus fistulosum resulted in a significantly greater amount of total phosphorus in plant shoots compared to non-mycorrhizal plants, although further increases in the percentage of root colonisation by the fungi had no effect on the plants. The presence of these mycorrhizal fungi had no effect on disease due to subsequent inoculation of the plants by P. fragariae. Increasing colonisation of Elsanta by Scutellospora nodosa was correlated with a significant increase in plant size and additional phosphorus uptake. However, these same plants exhibited greater levels of disease due to the following inoculation with P. fragariae. A low level of root colonisation of Elsanta by Acaulospora scrobiculata caused significant increases in plant size and phosphorus uptake up to a threshold level of root colonisation beyond which further increases had no affect on the plant. The results are discussed in relation to the utilisation of specific strains of arbuscular mycorrhizal fungi as inoculants of micropropagated strawberry plants of particular cultivars with the potential to increase plant growth and reduce the level of disease due to soil-borne plant pathogens.