AM J RESPIR CRIT CARE MED 1999;160:S33-S37.COPD is a debilitating and progressive condition in which the airways become irreversibly obstructed and the lungs progressively damaged. Unlike asthma, we know little about the cells that initiate and drive this process. Research has shown that CD8 T cells are overrepresented in the lungs of patients with COPD and that they are inversely related to lung function. However, not all CD8 T cells are alike and subsets that make IFN-γ but not IL-4 (Tc1), IL-4 but not IFN-γ (Tc2) as well as those that make both (Tc0) have been described. This article focuses on the characteristics of CD8 T cell subsets and considers their potential contribution to chronic obstructive pulmonary disease (COPD). Kemeny DM, Vyas B, Vukmanovic-Stejic M, Thomas M, Noble A, Loh LC, OʼConnor BJ. CD8 T cell subsets and chronic obstructive pulmonary disease.