Asthma is a common chronic disease that can have a significant impact on individuals' daily lives. It is characterized by wheeze, shortness of breath, chest tightness, and cough secondary to airway inflammation and hyperresponsiveness to a variety of stimuli. Asthma is far more common in boys than girls during early childhood. The prevalence equalizes between the genders during adolescence and then switches to a female predominance in adulthood. This article reviews the epidemiology and possible pathophysiologic mechanisms for the observed differences in asthma between the genders. In practical terms, the impact of asthma may be different according to gender in terms of daily activities for children and adolescents. The implications of gender differences in asthma for the health professional will also be discussed.