This article reviews the recent advances made in adoptive cell transfer of T-cell receptor-engineered lymphocytes in animal models. This approach is currently being used for cancer immunotherapy. Improvements have been made to optimize the genetic sequences that direct the expression of the engineered T-cell receptors. Markers have been included in these genetic sequences that allow the cells to be imaged with PET imaging. This allows one to track the distribution of the cells in mice and eventually in patients. Advancements made in animal models are rapidly being translated into the clinic.