Special health considerations include many issues that affect travelers at both ends of the age spectrum. Pulmonary diseases may seriously alter the physiologic responses to both cabin pressures in commercial airliners and exposure to high altitudes, but many of these responses can be predicted by blood gas determinations and simple measurements of pulmonary function conducted at sea level. Cardiac events represent the most common and unpredictable health problems that threaten both serious morbidity and death for adult travelers. Diabetic travelers require insulin dosage adjustments during east-west travel and well-stocked travel kits with adequate supplies. Human immunodeficiency virus-infected travelers require consideration of their levels of immunosuppression at the time of immunizations and special precautions for preventing potentially chronic enteric infections. Young children pose similar questions, and there is the additional problem posed by a limited number of readily available antimalarial agents for pediatric use.