Exercise-induced bronchoconstriction (EIB), subgrouped as exercise-induced bronchoconstriction with asthma (EIBa) or without asthma, is defined as acute airway narrowing that occurs during or after exercise. EIB has been described mostly in patients with asthma and athletes. Prevalence differs according to the subjects studied, challenge methods, and EIB definition. In the general population, prevalence is approximately 5% to 20%. In EIBa, it can be as high as 90% of patients with baseline asthma. In athletes, reported rates range from 7% to 70%. Some of the risk factors for developing EIB are living in an urban environment, a family history of asthma and atopy, and environmental factors such as low humidity.