The role of the polypeptide proinflammatory cytokine IL-1 family represents a group of proteins that have contrasting and synergistic biologic responses. IL-1alpha and beta and their precursor forms are heavily involved in the enhancement of inflammation and host defense. Within this family of gene products, there is also a naturally occurring receptor antagonist, IL-1ra, as well as a family of receptor proteins that have differential signaling functions and activities. The study of these proteins in human disease, including allergic disease and type 1 hypersensitivity responses, has led to a better understanding of the underlying general inflammation associated with these syndromes and has provided opportunities to look at new forms of intervention in allergic disease and asthma.