It has been repeatedly noted by clinicians that psychological stressors appear to be associated with the expression of asthma in individuals who have a genetic vulnerability for developing the disease. While retrospective evidence has supported this clinical observation (Levitan 1985; Teiramaa 1986), the association between emotional stressors and illness onset can only be convincingly demonstrated using a longitudinal design (Mrazek 1988; Steinhausen et al. 1983). In 1985 the W. T. Grant Asthma Risk Study was designed to identify which physiological and psychological risk factors for asthma were most highly associated with eventual expression of the disease. Young infants who were genetically at risk for asthma were evaluated and their development was prospectively monitored. The primary objective of the longitudinal study was to identify risk factors for illness expression. If this were possible, these risk factors could then be targeted for intervention efforts designed to delay the initial onset of asthmatic symptoms. The ultimate objective of an effective intervention would be that for some children, the illness could be prevented completely.