Abstract: To demonstrate how different levels of confinement stress at different time interval can affect the immune system of white mice, differential white blood cell (WBC) count was performed considering with and without application of confinement stress to male and female mice using different chamber diameters (1.0 inch, 1.5 inches, and 2.0 inches) at different time intervals (1 hour, 3 hours, 5 hours and at full confinement). Control group (without confinement) and experimental group (with confinement) were considered. Thirty mice (15 males, 15 females) were used with blood sample collected. Prepared blood smear was stained with wright-giemsa and examined under light microscopy. Differential WBC count was performed to determine the number/percentage of each type of WBC (lymphocyte, monocyte, neutrophil, basophil and eosinophil).