We have produced a chimeric single-chain T cell receptor (TcR) that combines the specific antibody recognition function and TcR/CD3 signaling properties within the same polypeptide chain. This hybrid molecule consisted of a single-chain antibody combining site that was connected over a short spacer to the transmembrane and cytoplasmic region of CD3. When expressed on TcR- or TcR+ T cell hybridomas it could mediate recognition of relevent target cells and subsequent production of lymphokines; i.e. it could functionally replace the TcR/CD3 complex. Therefore, the single-chain TcR model presented here represents an interesting and useful means for the creation of T cells with new specificities.