A collection of 43 unclassified members of the Pasteurellaceae, most of which were obtained from lesions, were investigated using an extensive battery of phenotypical tests as well as by ribotyping. The isolates had been made from Anser anser forma (f) domestica (d), Agapornis fischer, Amazona spp., Ara macao, Columba livia f.d., Melanopsittacus undulatus, and Psittacus erithacus. Comparison of results with those obtained from reference strains allowed classification of 25 strains. Three strains were identified as Pasteurella dagmatis, P. sp. A, and [P.] aerogenes, respectively. Twenty strains were classified as taxon 3 and two as taxon 14. Eighteen strains, all originating from psittacine species, belonged to two new taxa, tentatively named Bisgaard taxon 33 and taxon 37. Characters obtained with taxon 33 allowed classification within the family Pasteurellaceae, while the final classification of taxon 37 remains to be investigated. The present investigation underlines the problems confronting diagnostic laboratories attempting to identify members of the family Pasteurellaceae isolated from birds.