Tumour infiltrating lymphocytes (TIL) represent a targeted response of the adaptive immune system to the presence of tumour. This immunogenicity can be manipulated by tumour to encourage immune evasion and tumour growth. In some cases, the host’s immunity confers protection, and tumour infiltration by local immune cells is related to improved patient prognosis and survival. We present a short review of TIL and their prognostic importance to a number of tumours found throughout the body.