Genetic polymorphisms influence the magnitude of the cytokine response after the occurrence of various inflammatory stimuli. The pathophysiology of asthma involves, in part, the inflammation of the airway epithelium. Tumor necrosis factor (TNF)-α, a proinflammatory cytokine, is released into the airway and serum of patients with asthma. Indeed, higher serum levels of TNF-α have been demonstrated in children with active disease. We tested the hypothesis that children with asthma have genetic polymorphisms in the regulatory region of the gene coding for TNF-α that are associated with higher levels of TNF-α.