CD1d-restricted T-cell receptor Vα-invariant natural killer T (NKT) cells are important regulators of immune responses through their efficient secretion of T helper 1 (Th1) and Th2 cytokines. Recently, it has been shown that this NKT-cell population contains functionally distinct subsets, producing different sets of cytokines and cytotoxic effector molecules. NKT-cell subsets are also distinct from each other in their expression of adhesion molecules and chemokine receptors, suggesting that they might be targeted to different tissues and perform different immune functions.