Abstract: The present invention relates to polypeptides which are covalently bound to molecular scaffolds such that two or more peptide loops are subtended between attachment points to the scaffold. In particular, the invention describes peptides which bind to natural killer (NK) cells. The invention also includes multimeric binding complexes comprising at least two of said bicyclic peptide ligands. The invention also includes pharmaceutical compositions comprising said peptide ligands or said multimeric binding complexes and the use of said peptide ligands, multimeric binding complexes and pharmaceutical compositions in preventing, suppressing or treating a disease or disorder mediated by natural killer (NK) cells, such as inflammatory disorders, autoimmune disease and cancer.