Fourty-two human isolates that had been designated Pasteurella, or pasteurella-like organisms in the bacteriological routine laboratory were phenotypically characterized considering conventional, morphological and physiological features, and respiratory quinones. Thirty-seven of these strains fitted into the large traditional species, P. multocida, the majority of them being associated with alterations of the respiratory tract, and the rest with intestinal diseases, or putrid wound secretions mostly following animal bite or scratch lesions. Two strains isolated from sputum, or sinus maxillaris punctate, respectively, were P. ureae, and one strain recovered from a septicemic blood samle proved to be Cardiobacterium hominis. A pasteurella-like strain isolated from putrid sputum and an unusual organism that had been isolated from the cerebrospinal fluid of an infant with putrid meningitis remained unidentified. The bacteriological data are discussed with respect to the diagnostics of Pasteurella and similar organisms and especially, the range of phenotypical variation within the species, P. multocida.