Respiratory disease in swine has been increasing as production methods intensify. As the swine industry becomes more competitive and profit margins continue to narrow, the impact of respiratory disease on production and profitability will be of major importance. Veterinarians must be able to diagnose, treat, and most importantly, consult with producers to prevent these management diseases. Respiratory disease in swine presents the practitioner with a challenging diagnostic problem. The etiology is often multifactorial and involves complex interrelationships between host, pathogen(s) and environment. The environment of intense production facilities is of major importance in respiratory disease. Such factors as temperature, ventilation and animal flow and density should be included in diagnostic investigations.