Interest in the role of TNF-α in refractory asthma has been increased by a study showing increased concentrations of TNF-α in BAL from patients with more severe asthma and by an uncontrolled study showing that treatment with the recombinant soluble TNF-α receptor etanercept markedly improved AHR in patients with refractory asthma (Howarth et al., 2005). This evidence concerns the gene TNF and asthma.