Atypical Aeromonas salmonicida has been associated with ulcerations in several fish species but reports on slow-growing fastidious forms of Aeromonas salmonicida are relatively new. The 46 strains studied were isolated from ulcers of dab collected in 1992 and 1993. The isolates originated from 12 different sampling areas. Regardless of the geographic origin, all the strains exhibited homologous biochemical, physiological and drug resistance characteristics. The results indicated that dab isolates diverge from the type strains of A. salmonicida subsp. salmonicida and subsp. achromogenes.