The present invention relates to HLA-A*02-restricted cellular epitopes within the VP1 polypeptide of a human polyomavirus, BK virus, which is associated with polyomavirus-associated nephropathy in kidney transplant patients. Preferred peptides correspond to amino acids residues 107-116, 108-116 and 44-52 of BKV VP1, and are processed in vivo in natural infection with BKV. Effector T cell populations stimulated by the peptides represent functional CTLs as assessed by cytotoxicity and cytokine production, and are reactive against cells presenting both the BKV peptides above and the JC virus homolog sequences.