A total of 147 "Campylobacter-like" strains were isolated from six drinking water treatment plants within a two year investigation period. The strains were characterized by bio-, and serotyping according the scheme for Arcobacter butzleri. The result was that 100 strains were typed as Arcobacter butzleri, 17 strains as Arcobacter butzleri-like and 6 strains as Campylobacter jejuni/coli. 24 strains were typed as Arcobacter spp. The strains isolated from the treatment plants showed the same serotypes as described for human isolates. Therefore the spread of Arcobacter organisms via the drinking water path must be suspected.