Progress in genetics now enables the synthesis of molecules acting on the regulation of the immune system which are called cytokines. Currently there are several cytokines, Interferon (IFN), Interleukin 2 (IL2), tumour necrosis factor (TNF) as well as haematopoietic growth factors and these are the object of study in clinical trials. Interferon has already been used in the therapy of hairy cell leukaemia, Kaposi sarcoma associated with AIDS(SIDA) and metastasis of malignant melanoma. Interleukin 2 allows for an increase in the cytotoxic activity of NK cells in producing LAK cells, the lymphocyte infiltrating the tumour (TIL). Therapeutic combinations combining IL2 associated with LAK or of TIL have been evaluated in some private studies. These treatments have shown some interesting response levels on those tumours which are usually resistant, such as malignant melanoma or carcinoma of the kidney. TNF is active in vitro on human tumours; its potential toxicity is important; it is the object of a phase 1 clinical trial. Haematopoietic growth factors, G-CSF and GM-CSF, stimulate the production of leucocytes which will be valuable to correct toxic affects on the marrow during chemotherapy. This will enable chemotherapy to be given at a high dose.