The present invention relates to T cell receptors (TCRs) which bind the HLA-A*02 restricted peptide SLYNTVATL (SEQ ID NO : 1) derived from the HIV Gag gene product, p17. Said TCRs comprise non-natural mutations within the alpha and/or beta variable domains relative to a native HIV TCR. The TCRs of the invention possess unexpectedly high affinity, specificity and sensitivity for a complex of SEQ ID NO : 1 and HLA-A*02, and drive a particularly potent T cell response. Such TCRs are particularly useful in the development of soluble immunotherapeutic reagents for the treatment of HIV infected individuals.