Infants will be enrolled into this study in one of three groups. First, there will be a group of full term infants with no history of wheezing. Second, there will be a group of infants receiving a ct scan that is non-respiratory related. Third, there will be a group of infants that are born full term but have a history of wheezing of at least 3 episodes. The three groups will be compared to see if there is a difference in lung function, lung structure and lung size. Besides comparing the testing results we will be evaluating environmental and inherited characteristics. There are 2 purposes of this study. The first purpose is: To determine whether asymptomatic groups of infants at high risk for wheezing (Environmental tobacco smoke (ETS) exposure, Fm Asthma, male Gender) have fixed or reversible airway narrowing. The second purpose of this study is: To determine the relative contributions of fixed and reversible airway narrowing in infants with recurrent symptomatic wheezing, and to determine whether fixed and reversible airway narrowing is related to ETS exposure, Fm Asthma, and male Gender.