There are three phases of cohort follow up. First, mothers and children undergo an in-person wellchild follow-up visit during the child's second year of life conducted in the Vanderbilt Clinical Research Center, or during a home visit. Second, families are re-contacted every 12-18 months by phone and/or mailings for purposes of cohort retention, and to provide reminders about the remaining study components. Third, mothers, or the current guardians, undergo a phone interview during the fourth and sixth years of life to identify children with asthma, transient wheezing, AR and eczema.