Topical delivery of medications to the airway as medical aerosols is the first line treatment of asthma. Medical aerosols are produced by a range of devices and each device has its own characteristics, method of operation, and target patient population. Aerosol delivery can be a challenge as the structure of the airways is designed to minimize lung penetration of many aerosols found in the air around us; from dust and pollen to airborne pathogens. The smaller the airway, the greater the flow turbulence and therefore, the greater the volume of particles filtered. Thus, delivery of medical aerosols to children is often an order of magnitude less than adults [1]. This challenge is greater in asthma when there is airflow limitation, inflammation, excess mucus secretion, and airway remodeling [2]. Patient education for proper device use is as critical as proper device selection for effective therapy [3, 4]. In this chapter, we discuss the characteristics of aerosol devices and the best techniques for aerosol delivery in patients with asthma.