Three Phytophthora species were isolated from a demonstration plot of red raspberry in which the incidence of root rot and cane death was high. One of these was P. megasperma var. megasperma and all three were compared to P. cactorum, P. cambivora, P. cinnamomi, P. citricola, P. erythroseptica and P. fragariae in pathogenicity experiments to determine their importance in raspberry pathology. The mean increases in height of young primo canes 76 and 106 days after inoculation showed that only P. erythroseptica significantly depressed growth. The effect was enhanced when plants were transferred to a higher temperature for 14 days before measurements were made. A significant decrease in the mean size of the root systems occurred only when the inoculum was P. erythroseptica. Combined inocula of any two or all three of the species isolated had no greater effect on cane growth than single inocula. The implications of these results in relation to plant death in the demonstration plot and the importance of the environment in symptom expression are discussed.