Abstract: The present invention relates to a method for determining the hematopoietic cytocapacity of a subject comprising the steps of: (a) determining the amount of leukocytes present in a blood sample obtained from a subject, wherein said subject has been subjected to administration of a single dose of G-CSF and has been maintained for a time sufficient to allow mobilization or release of the leukocytes from hematopoietic production and storage tissues and sites of margination into the blood; and (b) determining the hematopoietic cytocapacity by assessing the amount of leukocytes determined in step (a) with the amount of leukocytes which have been mobilized or released in a control subject wherein said control subject is selected from the group consisting of subjects having (i) a high risk for a disease, disorder or complication associated with high-dose cytotoxic chemotherapy and/or hematopoietic cell transplantation, (ii) an intermediate risk for a disease, disorder or complication associated with high-dose cytoto