Extracts of some spices have been reported to play a contributory role in enhancing immune function. We evaluated and compared the effect(s) of single and combined oral administration of fresh aqueous onion (Allium cepa) and garlic (Allium sativum) extracts at different concentrations on some immunological determinants in rats. CD4 cells of the rats were estimated using Partec flow cytometric technique, while total and differential white blood cell (WBC) counts were estimated using the SysmsexR automated haematology analyzing technique. Our findings revealed that, CD4 and total WBC counts were significantly increased (P.0.05) in a dose-dependent manner in both onion (250mg/Kg/d: 349}11cell/ul and 2.75}0.15X103cell/l; 500mg/Kg/d: 389}10cells/ƒÊl and 3.05}0.05 X103cell/l; 750mg/Kg/d: 600}11cell/ƒÊl and 3.25}0.05X103cells/l) and garlic (250mg/Kg/d: 410}10cell/ul and 2.85}0.15X103cell/l; 500mg/Kg/d: 494}32cells/ƒÊl and 3.30}0.10 X103cell/l; 750mg/Kg/d: 684}11cell/ƒÊl and 3.55}0.05X103cells/l) treated rats when compared to the zero control (200}11cells/ƒÊl and 1.55}0.05X103cells/l, respectively). Extract of garlic at 750mg/Kg/d had significantly increased the CD4 cells and total white cell count when compared to other concentrations (P.0.05). However, no significant effect was observed on these parameters when extracts were combined (250mg/Kg/d: 252}21cell/ƒÊl and 1.80}0.10X103cells/l; 500mg/Kg/d: 315}21cells/ul and 2.10}0.10X103cells/l; 750mg/Kg/d: 368}10cells/ƒÊl and 2.35}0.05X103cells/l, respectively), the differential WBC count showed a significant increase in the proportion of cell types (lymphocytes, neutophils and monocytes) (P.0.05). The results from this study revealed the immune boosting capabilities of Allium cepa and Allium sativum, but underscored their synergistic activities.