We designed oligonucleotides to differentiate between the seven currently known Capnocytophaga species. The oligonucleotides were labelled non-radioactively at the 3' end with digoxigenin. The specificity could be demonstrated in a dot-blot hybridization assay by using the type strains, reference strains, and 37 clinical Capnocytophaga isolates as well as 11 representative strains of other taxa as a template. The sensitivity of the assay was calculated with 10(3) bacteria per dot.