Activity of calmodulin and uptake of Ca2+, Na+ and Cl- was studied in control and Giardia lamblia infected mice. The activity of calmodulin was found to be significantly increased (p less than 0.001) in the experimental group as compared to control group. The uptake of Ca2+ increased significantly (p less than 0.001) while that of Na+ and Cl- decreased (p less than 0.001) in brush border membrane (BBM) vesicles from experimental group as compared to control group. In the presence of calmodulin inhibitor, trifluoperazine (TFP), the transport of Na+ and Cl- increased significantly (p less than 0.05) as compared to in the absence of inhibitor while transport of Ca2+ remained unaltered.