The effects of protein, pH, temperature, sodium chloride (NaCl), clays, sucrose, and their interactions on the survival and growth of Pasteurella multocida were evaluated. Pasteurellae populations declined rapidly in waters maintained at 2 C, compared to 18 C. Increasing water soluble proteins by 175 μg/ml, and NaCl by 0.5%, greatly enhanced survival of P. multocida, whereas variations in pH, clays, and sucrose had relatively minor effects. Pasteurella multocida survived for over 1 yr in some samples of water. This is the longest known survival of these bacteria in water.