Abnormal expression of key signaling molecules and defective functions of T lymphocytes play a significant role in the pathogenesis of systemic lupus erythematosus (SLE). T-cell receptor (TCR)/CD3-mediated stimulation of SLE T cells shows increased protein tyrosine phosphorylation of cellular proteins, with faster kinetics, heightened calcium response, and decreased interleukin (IL)-2 production. The molecular mechanism of T-cell signaling abnormalities in SLE T cells is complex and cannot be explained fully by the current theories of T-cell signaling. Current research on lymphocyte signaling abnormalities in SLE has been directed toward investigating various factors that contribute to abnormal tyrosine phosphorylation, intracellular calcium response, and cytokine production. Latest developments suggest multiple components, including altered receptor structure, supramolecular assembly, modulation of membrane clustering, aberrant cellular distribution, and precompartmentalization with lipid rafts invariably contributing to abnormal T-cell signaling in SLE T cells. The methods and protocols described here pertaining to T-cell signaling abnormalities in SLE T cells are very much optimized in many ways, and they were derived by the combined tasks and continuous efforts of many researchers in the laboratory over a long period. These simplified protocols can be readily applied to study T-cell signaling abnormalities in SLE to identify the genetic, molecular, and biochemical factors contributing to aberrant immune cell function and unravel the pathophysiology of SLE.