Seventy-eight strains of Vibrio anguillarum serovar O1, all harboring one 65- to 70-kilobase plasmid, were typed according to restriction fragment length polymorphism of the plasmid. Six types, three of which comprised 96% of the strains examined, were produced with the restriction endonuclease BamHI. The fragment length polymorphism type did not correlate to any of 12 different phenotypic properties tested.