The acute phase protein (APP) response was evaluated after prolonged transportation of pigs under commercial conditions. Elevated serum APP concentrations were observed in two groups of boars immediately after their arrival at a destination farm compared with within-animal control samples obtained one month later. The effect was more pronounced in the first group of pigs conveyed under average transport conditions (Transport 1, 24 h), although the second group was transported for a longer time period (Transport 2, 48 h) but in superior transport conditions. In a second trial, pigs were sampled before transport, on arrival at an abattoir (following 12 h transport), and at the slaughter-line (after 6 h lairage). Significant increases in major acute phase protein (Pig-MAP), haptoglobin, serum amyloid A, C-reactive protein, and a decrease in apolipoprotein A-I, were observed at slaughter. The results demonstrate that shipment of pigs by road can result in an APP response that is probably related to the stress of transport.