In this study, three groups of New Zealand White rabbits, 6-8-week-old, were inoculated with Pasteurella multocida serotype 3:A strain of rabbit origin by routes of intranasal, intratracheal and intravenous inoculations, respectively. The animals died or killed after the 4-6, 8-10 and 14 days of observation periods were necropsied. All of tissues were examined macroscopically and microscopically. In addition, pulmonary lesions were examined with electron microscopically. Pneumonic lesions were detected most consistently in rabbits inoculated intratracheally. Intranasal inoculation was less effective than intratracheal inoculation. The lesions were minimal in intravenous dosed group. All of the routes of Pasteurella multocida serotype 3:A inoculations produced especially the lower respiratory tract lesions. Pulmonary lesions were observed in %50 of animal inoculated intranasally, %75 of animals inoculated intratracheally and %17 of animals inoculated intravenously. The histological examinations revealed severe fibrinopurulent and necrotic pneumoni, fibrinopurulent pleuritis and fibrinopurulent pericarditis. Pasteurella multocida were shown electron microscopically in free manner in alveolar spaces, in phagocytic vacuoles of cytoplasm of neutrophilic granulocytes in alveolar spaces and in alveolar capillary lumens. As a result, Pasteurella multocida 3:A serotype can induce pneumonia in rabbits through different routes of inoculation: intratracheal, intranasal, and intravenous. However, intratracheal inoculation is the most effective method to induce pneumonia while intranasal inoculation is the second most and intravenous inoculation is the least effective.