The response of four positive acute phase proteins (APP) was evaluated in pigs after co-infection with swine influenza virus (SIV) and Bordetella bronchiseptica (Bbr). Twelve piglets from a herd with high health status were used. Eight of them were infected intranasally with SIV and Bbr. The standard bacteriological methods for detection of Bbr and PCR tests for identification of Bbr and SIV in nasal swabs, lungs and bronchoalveolar fluids were used. serum APP concentrations were measured using commercial ELISA tests. Various kinetics of response was identified within the APP tested. C-reactive protein (CRP), serum amyloid A (SAA) and pig major acute protein (Pig-MAP) were characterized as fast and transient responders, while haptoglobin (Hp) as a fast but very prolonged responder. The significant correlation was found between concentrations of Hp and SAA in the serum and degree of turbinate atrophy as well as changes observed in the lungs. On the basis of our investigation we state that evaluation of Hp and SAA concentrations in the serum of pig co-infected with SIV and Bbr may provide useful information about severity of changes observed in the turbinates and lungs. Moreover, since all investigated APP strongly reacted after co-infection, it is clear that APP-measurements may reveal ongoing infection in pigs and could be the primary screening test prior to specific disease diagnosis. Future studies should focus on the possibility of distinguishing infected and non-infected pigs under field conditions.