Asthma symptoms often develop during the first years of life. Longitudinal studies show that at least 40% of children with wheezing lower respiratory illnesses (LRIs) during the first 3 years of life still have wheezing episodes at 6 years of age. Thus, it is important to identify children at risk of developing asthma, and to distinguish these from those in whom early wheezing is likely to be transient. This is complicated, however, by the variable nature of asthma and the lack of specific and sensitive markers. Genetic markers and epidemiologic risk factors for asthma have been identified, but cannot be used to predict the development of asthma in an individual patient. Similarly, infants who subsequently develop asthma in childhood have higher serum immunoglobulin E (IgE) and peripheral eosinophil counts than those who do not develop asthma, but, again, these factors are not sufficiently sensitive and specific to allow identification of children at risk of developing asthma. An algorithm is presented that outlines possible criteria to determine the risk of developing asthma in infants.