We undertook an analysis of the genomic relationships between 15 isolates of Phytophthora ramorum Werres, de Cock et Man in't Veld, obtained from symptomatic plants growing in Polish ornamental nurseries, and 2 representatives of the European population and 3 of the North American population. Dendrograms were generated by UPGMA based on 786 amplification products obtained in ISSR-PCR reactions. The representatives of the European population and 13 of the 'Polish' isolates formed a common cluster. The other 2 ?Polish' isolates, which were found in 1998, and the 3 American representatives formed 2 separate clusters. There was no observed link between genomic distance on the basis of polymorphism and the origin of the isolates from plant species.