Forty-eight Pasteurella multocida cultures collected from rabbits over a 56-year period were examined to determine their physiological characteristics and to determine their serological types in the gel diffusion precipitin test. Generally, the physiological characteristics from 30 tests were typical for P. multocida. There were a few atypical variations in the fermentation of lactose and maltose and variations in trehalose, dulcitol, xylose, sorbitol, and glycerol. Seven cultures did not produce indole, and four cultures did not produce detectable amounts of hydrogaen sulfide. In obliquely transmitted light, 26 cultures formed large, slightly iridescent, mucoid colonies, 17 cultures had iridescent colonies, and 5 cultures had blue colonies. Heat-stable antigens from the 48 cultures reacted with antisera prepared from P. multocida type cultures presenting serotypes 1, 3, 4, 12, and 15. Antigens from 15 cultures reacted slightly with antisera from more than one serotype. Overall, gel precipitin reactions involving serotype 3 (25%) and serotype 12 (66.7%) were the most prevalent.