Millions of people worldwide suffer from respiratory diseases, such as allergies, asthma and chronic obstructive pulmonary disease (COPD), and these diseases constitute a major public health burden. The latest statistics from the World Health Organization (2007) estimate that 300 million people worldwide have asthma, 210 million people have COPD and millions of people are affected by allergies. The prevalence of these diseases is increasing, and there is a continued need for new and improved therapies.

This Focus issue of Nature Reviews Immunology highlights the latest advances in our understanding of the immunological bases of these respiratory diseases and how this knowledge can be translated into effective treatment strategies. Donata Vercelli (page 169) describes the techniques used in, and the recent results from, genetic studies that have identified susceptibility genes for asthma and asthma-related traits. Peter Barnes compares and contrasts the immunology of asthma and COPD (page 183). Hamida Hammad and Bart Lambrecht review the crosstalk between dendritic cells and epithelial cells in the induction of asthma (page 193). Hannah Gould and Brian Sutton outline the role of IgE in allergy and asthma (page 205). And finally, Stephen Holgate and Riccardo Polosa (page 218) describe the current treatment strategies for asthma and allergy, and highlight the new strategies that hold promise for the future.

In our Research Highlights section, we highlight several topics related to the theme of allergy and asthma, including the role of signals from eosinophils and basophils in the induction of T-helper-2-cell responses, and the importance of breastfeeding in protecting against the development of allergic airway inflammation.

We hope that you enjoy this special Focus on Allergy and Asthma.