This review examines the effects of handling by humans and housing systems on physiological stress and some consequences in swine. Small amounts of threatening behavior by humans, imposed either regularly or irregularly, can produce a chronic stress response, as evidenced by increases in plasma free corticosteroid concentrations resulting in adverse effects on avoidance behavior, growth and reproductive performance. Housing systems involving a high level of confinement can result in a chronic stress response in swine with adverse effects on metabolism and the immune system. This stress response may be the result of unstable social relationships and can be ameliorated by the design of housing systems.