The prevalence of complex genetic immune disorders, such as asthma, arthritis and diabetes, has escalated in recent decades. Despite the formidable challenges posed by the identification of susceptibility genes in complex genetic disorders such as these, several groups have now progressed from broad linkage regions to the identification of several positional candidate asthma genes. The insights into disease mechanisms that these recent discoveries might allow will inform the development of new therapeutic strategies for the treatment of asthma and will pave the way for the identification of genes that underlie a diverse array of immunologically mediated disorders.