A hematology reference control containing an immature granulocyte component and the method of making are disclosed. The reference control includes an immature granulocyte component made of processed blood cells for simulating human immature granulocytes, and a suspension medium suitable for delivering the component to a blood analyzer for measurement of immature granulocytes. The immature granulocyte component can be made of processed avian, reptile or fish red blood cells, or human immature granulocytes produced in vitro. The reference control further includes a white blood cell component which includes white blood cell sub-components for simulating white blood subpopulations. Further disclosed is the method of using the reference control for measurement of immature granulocytes on a blood analyzer.