Throughout the 12 months of treatment, all participants will receive albuterol to treat respiratory symptoms and prednisolone if asthma symptoms worsen. Parents will be given an action plan to help manage their child's symptoms, and during respiratory illnesses, parents will contact study researchers to determine the best treatment plan. Study visits will occur at baseline and Weeks 4, 12, 20, 28, 36, 44, and 52. Participants' parents will take part in scheduled telephone interviews one month after each clinic visit to provide information on their child's asthma symptoms, study medication use, and health problems. Most study visits will include a physical exam and lung function testing. At select study visits, the following will occur: allergy skin testing, blood collection, nasal mucus sampling, and parent questionnaires to assess asthma, quality of life, and environmental factors. A portion of the participants' blood will undergo genetic analysis; a blood collection from parents for genetic analysis will be optional. Throughout the treatment period, participants' parents will record asthma symptoms and medication usage in a daily diary.