Although small amounts of stress can yield benefits such as increased alertness and an improved ability to concentrate, an accumulation of stress caused by daily frustration and major life events has been associated with numerous health problems. In studies of flight crew members, stress has been associated with pilot error. _______________________________________________ Stress is the body’s response to demands, pressures or changes. Causes of stress (stressors) can be major life events, such as a death in the family or a new job; ongoing aggravations, such as a chronic illness or an inflexible work schedule; or the annoyances of daily life, such as traffic jams or — to crew members — exposure to aircraft engine noise and vibration during flight. Each encounter with a stressor causes a complex reaction that begins with a signal from the brain to the autonomic nervous system, which controls involuntary body functions such as breathing, heart rate and blood pressure. The signal from the brain also triggers the release of hormones — primarily adrenaline and noradrenaline (also known as epinephrine and norepinephrine) from the adrenal glands — into the bloodstream to prepare the body to cope with a perceived danger.1 In response to the brain’s signal, the breathing rate increases to allow the body to take in more oxygen, and the heart rate increases, blood pressure rises, and some blood vessels narrow, directing blood to the muscles and brain and away from the skin and other organs not involved in the response to the perceived danger. Some blood cells (platelets) become “stickier” (more adhesive) to prevent excessive bleeding in the event of injury. Fats and glucose (sugar) are released from storage sites to provide energy, and muscles become tense. Long ago, the stress response was vital in fighting off enemies and running from predatory beasts (the “fight-or-flight” response). However, the stress response typically occurs today in situations that are considerably less than life-threatening; repeated activation of the stress response, rather than providing the impetus to fight or to flee danger, may contribute to serious health problems.