[en] The objective was to establish a chronic pneumonia model in swine using pseudorabies virus (PRV) and Pasteurella multocida (Pm) and to study this interaction. Exp. 1: five groups of five pigs (six wk old) were assigned randomly and housed in isolation units. Group 1: virulent PRV (10 /SUP 3.5/ cfu/pig), seven days later Pm (10⁹ bacteria/pig) and euthanatized after seven more days. Group 2: vaccinial PRV and then Pm (same times and dose). Group 3: PRV only. Group 4: Pm only. Group 5: unioculated control. In Group 1, 3/5 animals had lesions, as well as 1/5 in Groups 2, 3 and 4 and 0/5 in Group 5. Lesions in Group 1 were more extensive (P<0.05). Pm was isolated from 3/5 and 1/5 from Groups 1 and 4 and 0/5 from groups 2, 3 and 5. Exp. 2: six groups of either six pigs (inoculated) or four pigs (controls) each. Group 1: PRV (10 /SUP 3.5/ cfu/pig) and Pm as in Exp. 1. Group 2 PRV (10 /SUP 4.5/ cfu/pig) and Pm. Group 3 PRV (10 /SUP 5.5/ cfu/pig) and Pm. Group 4: PRV only (10 /SUP 5.5/ cfu). Group 5: Pm only. Group 6: control. Lesions recorded were: 4/6 Group 1, 5/6 Group 2, 6/6 Groups 3 and 4 and 0/6 Groups 5 and 6. Isolations of Pm were 3/6, 4/6, 6/6, 1/6, 0/6 and 0/6, respectively. PRV impairs the host's defenses allowing Pm to colonize the lung and the effect of PRV is dose dependent. A further experiment was performed to assess the effects of PRV on clearing of Pm by alveolar macrophages (AM) obtained from lung lavage with PBS of two, six wk old conventional pigs. AM were cultured in vitro in plastic wells (10⁶ cells/well) for 48 to 72 hr