Because of the imminent market opening of livestock and poultry products, Korean poultry industry is faced an influx of contagious diseases from abroad. Due to the increasing trend of intensive and automatic poultry farming, the risks of catching various poultry epidemics are ever more increasing. For the prevention of poultry epidemics, the principles of biosecurity should be observed rather strictly. In addition, regular checking to confirm the presence or absence of latent diseases through serological test, post-mortem examination, and laboratory test, should be carried out routinely. Finally, all kinds of stress factors should be minimized to keep the flock healthy and productive, so that they can achieve their maximum genetic potential.