The idea that an abnormality in the beta(2)-adrenergic receptor contributes to asthma has been a long-standing hypothesis. Since the discovery of functionally relevant polymorphisms in the beta(2)-adrenergic receptor gene, there has been intensive research on their impact on asthma and related phenotypes, particularly the responsiveness to bronchodilators. It is the aim of this chapter to summarize the latest developments in this interesting field of research.