Zoospores and agar discs of the fungus causing raspberry root rot (P. fragariae) were used as inoculum to assess the resistance of raspberry genotypes in pot experiments. High zoospore concn resulted in more severe symptoms than low concn. There was a strong correlation between the results obtained with zoospores and with colonized agar discs as inocula, although disease was generally more severe with the former. The severity of root rot was correlated with a number of other symptoms, in particular growth reduction, stem lesions and leaf wilting, and some of these symptoms could possibly be used as measures of resistance. There was no evidence of physiological specialization with the range of isolates and raspberry genotypes used. Pot tests in general gave results which matched reported resistances in the field, and could be used to assess the resistance of breeding lines and selections.