The present invention provides T cell receptors (TCRs) having the property of binding to SLLMWITQC-HLA-A*0201, the SLLMWITQC peptide being derived from the NY-ESO-1 protein which is expressed by a range of tumour cells. The TCRs have a KD for the said that peptide-HLA complex of less than or equal to 1µM and/or have an off-rate (koff) of 1x10<-3> S<-1> or slower.
