Bacterial strains isolated from cankers of wild cherry trees (Prunus avium) in France were characterized using numerical taxonomy of biochemical tests, DNA-DNA hybridization, repeat sequence primed-PCR (rep-PCR) based on REP, ERIC and BOX sequences, heteroduplex mobility assay (HMA) of internal transcribed spacer (ITS) as well as pathogenicity on wild cherry trees and other species of Prunus. They were compared to reference strains of Pseudomonas syringae pathovars isolated from wild and sweet cherry and various host plants. Wild cherry strains were closely related to P syringae (sensu lato) in LOPAT group la (+ - - - +). Wild cherry strains were pathogenic to wild cherry trees and produced symptoms similar to those observed in orchards. They were pathogenic also, but at a lesser extent, to sweet cherry trees (cv. Napoleon). The wild cherry strains were collected from five different areas in France and appeared to constitute a very homogeneous group. They showed an homogenous profile of a biochemical and physiological characteristics. They were closely related by DNA-DNA hybridization and belonged to genomospecies 3 'tomato'. Rep-PCR showed that wild cherry strains constitute a tight group distinct from P.s. pv. morsprunorum races 1 and 2 and from other P syringae pathovars. HMA profiles indicated that the ITS of all wild cherry strains were identical but different from P.s. pv. persicae strains since the two heteroduplex bands with reduced mobility were generated by hybridization with the P.s. pv. persicae pathotype strain CFBP 1573. The 8 genomospecies of Gardan et al. (1999) have not been converted into formal species as they cannot be differentiated by biochemical tests. Therefore, the pathovar system within P syringae was currently used. P syringae pv. avii is proposed for this bacterium causing a wild cherry bacterial canker and strain CFBP 3846 (NCPPB 4290, ICMP 14479) is designated as the pathotype.