The role ofPhytophthoraspecies in the development of root rot in kiwifruit was investigated. Seven species were isolated from soil samples collected from the base of unhealthy kiwifruit vines in six orchards in the Auckland region, New Zealand, using a soil baiting technique. The species were identified asPhytophthora cinnamomi,P. citricola,P. cryptogea,P. gonapodyides,P. megasperma,P.sterile A andP.sterile B. With the exception ofP. megasperma, all species were pathogenic against 9-month-old kiwifruit plants in glasshouse tests. In particular,P. cryptogeaandP. cinnamomiwere highly virulent causing extensive rotting of the fine fibrous roots of rootstocks of cultivars Hayward and Bruno. Cultivar Hayward was more susceptible to infection than Bruno by four of the six pathogenic species.