Lymphokine activated killer (LAK) cells are being considered as a new and promising form of immunotherapy in the management of patients with solid tumours. Few informations are instead available on these cytotoxic effectors in haematological neoplasias. Here we shall discuss the possible role of LAK cells in human leukaemias. Evidence will be provided for a rationale in the clinical exploitment of Interleukin 2 (IL2)/LAK cells in the treatment of acute leukaemia patients, whilst the implication of these cytotoxic populations appears more uncertain in chronic lymphoproliferative disorders.