Allergy and asthma are related conditions caused by a complex interaction of genetic factors and environmental influences. With family data from several different populations, linkage analysis has been performed and used to identify regions of the genome that contain susceptibility genes for these conditions. To date, 4 genome screens have been completed and have successfully identified several chromosomal locations that are likely to contain asthma and allergy genes. Many of these regions contain potential biologic candidate genes that modulate immunologic responses or airways inflammation. By focusing on the common regions that have been replicated in these 4 genome screens, the major susceptibility genes for asthma and allergy should be identified. This will lead to an improved understanding of pathogenic factors that lead to development or progression of asthma and allergic diseases. (J Allergy Clin Immunol 2000;105:S477-81)