The taxonomy and virulence of four unknown bacterial isolates (11S9306, 16S9306, 12E9306, 13E9306) associated with erytrodermatitis-like symptoms of carp have been examined. The isolates differed from currently known bacteria pathogenic for carp. Characteristics of the isolates were nearly identical with those of Chromobacterium violaceum. Differences concern indole production and d-mannitol utilization (isolates+, Ch. Violaceum -). In virulence tests (subcutaneous injection of 1x10⁷ cfu, and intraperitoneal injection of 5x10⁵ cfu) the isolates appeared to be more pathogenic than pathogenic strains of Aeromonas hydrophila and A. salmonicida var. achromogenes. This phenomenon was a little more pronounced at 21°C than at 13°C.