Major progress has been made during the past few years in developing a better understanding of the genetic basis of asthma, which has led to the identification of several chromosomal regions and loci showing linkage to and association with asthma and asthma-related phenotypes. Recent positional cloning approaches have also been informative in identifying several strong candidate genes for asthma. As another approach, association studies between candidate gene polymorphisms and asthma-related phenotypes have been conducted in many areas and replicated in different ethnic groups. These approaches need to be followed by validation processes to confirm their functional relevance in the pathophysiology of asthma. In this review, we describe several novel genes, including ADAM33, ADRB2, and eotaxin, that modify airway responsiveness in asthmatic patients.