Granulo-monocytic growth factors are important members of the family of growth factors which alter the biological response. These factors are glycoproteins and are hormones regulating the production of haematopoietic cells and show their adaptation to possible needs. There are four which are currently well recognised; they are now grouped collectively under the term colony-stimulating factor and of these two, GM-CSF and G-CSF are available thanks to genetic engineering and have reached the stage of therapeutic trials. It is essentially the treatment of solid tumours which should lead to the most profound changes in the current management of cytotoxic drugs because they may allow an increase of the dose and a shortening of the duration of the phase of neutropenia and thus the infection risk. In therapeutic pneumonology they would be able to be used as an adjuvant to chemotherapy in small cell cancers and available in protocols using polychemotherapy with a risk of marrow suppression, indeed even permitting the practice of intensified chemotherapy regimes with or without the support of bone marrow graft. However the clinical experience acquired using growth factors remains limited and is almost exclusively restricted to the haematological domain. Although the secondary effects appear tolerable their harmlessness--and notably the absence of a stimulating effect on tumour growth--remains to be shown before extension of their use will lead to any changes of therapeutic strategies.