G-CSF is a pleiotropic cytokine best known for its specific effects on the proliferation, differentiation, and activation of hematopoietic cells of the neutrophilic granulocyte lineage. It is produced by activated monocytes/macrophages, fibroblasts, endothelial cells, astrocytes, osteoblasts and bone marrow stromal cells. In addition, various carcinoma cell lines and myeloblastic leukemia cells can produce G-CSF constitutively. G-CSF and G-CSF receptors have also been shown to be produced by placental, decidual and endometrial gland cells during pregnancy, suggesting that G-CSF may play a role in decidual and placental functions. Clinical use of G-CSF has been approved for the amelioration of chemotherapy-induced neutropenia as well as for severe chronic neutropenia following bone marrow transplants.