There are close correlation among environment and feeding management and porcine respiratory disease. Therefore, control the incidence of swine disease except focusing on pathogen, consider the environment factors and proper feeding managements to block the pathogens circulating in a pig farm is also very important. This project will select the pig farms with high and low postweaned rate respectively. The raising system (complete or batch production) of these farms will be discussed. Furthermore, beside the serum antibodies against different diseases of pigs from these farms will be measured. The pathogens will be isolated from carcasses of these farms too. Basing on these results, we will be aware of current pig diseases and vaccination status of the pig farms in Taiwan. It will help the animal health inspection unit to adopt suitable prevention and control measures. Moreover, to know the correlation between raising system and diseases in a pig farm could give the farmers another choice when they attempt to reduce the disease incidence rate. Therefore, it is helpful for the farmers to cut down their prime cost and face the impact of import pork in the future.