Recent studies in patients with systemic lupus erythematosus (SLE) have demonstrated that autoantigen-reactive T cells can be isolated from peripheral blood and that such cells can support autoantibody production ex vivo, suggesting that they may have a central role in the pathogenesis of disease. In addition, recent work has identified and characterized signaling abnormalities in T cells from SLE that may be fundamental to the disease. This review will examine the role of T cells in the pathogenesis of SLE and it will consider pathogenic mechanisms by which T cells escape normal of immunological tolerance. The focus will be on recent studies characterizing autoantigen-reactive human T cells and signaling abnormalities identified in T cells from patients with SLE.