T lymphocytes express on their surface a heterodimeric αβ receptor, called the T cell receptor (TCR), which recognizes foreign antigens. Unlike antibodies, the recognition requires both an antigenic peptide epitope and a protein encoded by the major histocompatibility complex (MHC). In contrast to conventional antibody-directed target antigens, antigens recognized by the TCR can include the entire array of potential intracellular proteins, which are processed and delivered to the cell surface as a peptide/MHC complex. In the past 10 years, there have been significant efforts to engineer TCRs in various formats, which would allow improved recognition and destruction of virus-infected cells or cancer. The proposed therapeutic approaches involve either the use of engineered, high-affinity TCRs in soluble forms, analogous to antibody-directed therapies, or the use of engineered TCRs whose genes are reintroduced into autologous T cells and transferred back into patients (T cell adoptive therapies). This chapter describes three methods associated with the engineering of TCRs for these therapeutic purposes: (1) use of a yeast display system to engineer higher affinity single-chain VαVβ TCRs, called scTv; (2) use of a T cell display system to engineer higher affinity full-length TCRs; and (3) expression, purification, and characterization of soluble TCRs in an Escherichia coli system.