Thrombopoietin (TPO) is primarily produced by hepatocytes and regulates the production and differentiation of megakaryocytes and platelets in the bone marrow. The endogenous TPO level is increased when the megakaryocyte count is low, and high in aplastic anaemia and after myeloablative chemotherapy. TPO is cloned and manufactured by a recombinant technique for clinical use. Treatment with recombinant human TPO (rhTPO) after intensive chemotherapy may reduce the need for platelet transfusions. Administration of granulocyte colony-stimulating factor in combination with rhTPO has enhanced the mobilisation and harvest product of haematopoietic stem cells. Whether rhTPO is effective in the treatment of the myelodysplastic syndrome, aplastic anaemia, and other conditions with bone marrow insufficiency (including AIDS) is not yet known. In liver cirrhosis, the endogenous TPO level rapidly increases after liver transplantation. Accordingly, substitution of rhTPO may be indicated in advanced liver failure complicated by thrombocytopenia and bleeding.