Alterations of serum zinc (Zn) and copper (Cu) concentrations are commonly found in patients suffering from gastrointestinal infections and with hepatic, renal, cardiovascular, and malignant diseases. In this study, the serum Zn and Cu levels in 20 children with giardiasis and in 40 children with amebiasis were evaluated. The serum Zn levels showed a significant decrease when compared to controls (p<0.001). After metronidazole therapy, a significant increase in Zn levels was observed (p<0.001). There was no significant difference in serum Cu levels between patients and controls before therapy. Before therapy, the serum Cu/Zn ratio in children with either giardiasis or amebiasis was significantly higher than that of the control group. After therapy, the Cu/Zn ratio was found to be back to normal. There were no significant differences in serum Zn levels and Cu/Zn ratios between children with and without diarrhea and there was no significant difference in children with or without failure to thrive. We concluded that Zn deficiency and elevated Cu/Zn ratio could be acute-phase responses to parasitic infections in children with giardiasis or amebiasis and that a successful treatment of the primary disorder will lead to complete recovery. Further studies are in progress to confirm the benefit of Zn supplementation during the acute phase of the disease, particularly in zinc-deficient regions of the world, such as in the case of Turkey.