Exercise-induced bronchoconstriction (EIB) can be a troublesome problem in asthmatic children and in some children without asthma. Self-reported exercise related symptoms should be verified formally. EIB is mediated by changes in temperature and humidity in the airway and is secondary to release of several mediators of the bronchoconstriction including leukotrienes. Montelukast as a leukotriene receptor antagonist offers protection against but does not completely ameliorate EIB. Regular use does not appear to lead to tolerance. Nightmares, abdominal pain, fever, nausea and aggressiveness are commonly described side effects; however, the overall safety profile of montelukast is good and does not change with long term use. There are individual differences in response to montelukast for protection against EIB. Bronchoconstriction triggered by exercise responds to cessation of exercise in its natural course. Due to its pharamacokinetic profile, montelukast may be more useful as a prophylaxis than to relieve symptoms.