The main characteristic of a superantigen (SAg) is that it activates specific subsets of T cells that are composed of particular T-cell receptor (TCR) variable region β chain gene products (TCRBV). SAgs are thought to form a bridge between the TCRBV region on the T cell and the MHC class II molecule on the antigen-presenting cell (APC). This bridging transduces a strong signal to the T cell through the TCR, resulting in T-cell activation, which is manifested by upregulation of cell-surface markers associated with activation, T-cell proliferation, and cytokine release. In this chapter we shall outline two methods for assessing specific T-cell activation based on the preceding criteria: 1) detection of markers of activation in individual TCRBV subsets early after SAg stimulation; and 2) analysis of cytokine release from TCRBV specific T-cell hybridomas in response to SAg presentation.