Summary The effect of induced inflammatory exudates upon the distribution and absolute number of granulocytes in the blood has been studied in human subjects. In normal subjects without inflammation/the mean size of the total blood granulocyte pool (TBGP) was 70 × 107 cells/kg with 31 × 107 cells/kg in the circulating granulocyte pool (CGP) and 30 × 107 cells/kg in the marginal granulocyte pool (MGP). The TBGP increased to 144 × 107 cells/kg in 8 subjects studied 2 to 3 hours after initiation of inflammation. The CGP did not change in size. All of the additional granulocytes in the blood were within the MGP. This type of blood granulocytosis has been termed “masked” granulocytosis since it is undetectable by enumeration of granulocytes in venous blood samples.