Since its discovery in 1993, the mitogen-activated protein (MAP) kinase p38 has attracted much attention for its role in a wide range of cellular processes, many of which involve the immune system. Although p38 has been heavily implicated in the function of all type immune cells, research has tended focus on its role in innate immunity. In this review we attempt to highlight some of the major discoveries that have been made regarding p38's role in adaptive immunity, and also to discuss the possible future implications of these discoveries.