Since the initial detection of T_H2 cytokines in asthmatic airways, our understanding of the complexity of T-cell subtypes and flexibility and of the potential role of airway structural cells in the immunopathology of asthma has increased. Cytokines derived from airway epithelium, including IL-25, IL-33, and thymic stromal lymphopoietin, might be important drivers of T_H2-type inflammation in asthma. The balance between effector T_H2 cells and suppressive regulatory T cells is skewed toward a proinflammatory T_H2 response in atopy and asthma, and there is much interest in how to redress this equilibrium. Novel T-cell subsets, including T_H17, T_H9, and T_H22, have been described, although their role in asthma remains unclear. Other T cells, including natural killer T cells, γδ T cells, and CD8 T cells, have also been implicated in asthma, although their importance remains to be confirmed. Therapeutic strategies aimed at T_H2 cytokines are beginning to bear fruit in patients with asthma, although like many biologic agents, these might need specific targeting at subgroups of patients. Strategies directed specifically at the T cells are currently being evaluated, including novel forms of allergen immunotherapy. T cells remain an exciting potential target for new treatments in patients with asthma.