Asthma is a complex genetic disease that is thought to result from a combination of genetic susceptibility and environmental exposures. Asthma most often develops within the first few years of life and identified risk factors include familial history of asthma, infantile atopic dermatitis, and skin test reactivity to a subgroup of allergens. It still is not clear whether the association with skin test reactivity reveals contributions to pathogenesis by enhanced tendency to produce IgE antibodies or enhanced tendency for T cells to polarize in a Th2 direction or whether these attributes simply act as markers of a condition the origins of which still have not been identified. Currently, severity and persistence have not been unequivocally linked to these (or other) factors. Although clinical remittance is common, recent studies suggest lung function deficits may persist in the absence of symptoms and contribute to risk for chronic obstructive pulmonary disease. Additional studies are needed to establish the mechanisms underlying the development of asthma so that preventive and cure modalities may be rationally developed.