The effect of diabetes on trace elements concentration in blood of experimental animals has been studied by thin-target X-ray fluorescence analysis. Balb/C young adult mice, 6-8 wk old, were used in the study. About 100-200 μL venous blood was taken from each mouse for trace element analysis. The measurements were carried out on a commercial Wave-Length-Dispersive XRF System, with different X-ray tubes being used for maximizing the detection sensitivity of different groups of elements.Later on, the mice were made diabetic by an intravenous injection of Streptozotocin (250 mg/kg). Then, 2 and 3 wk after the injection, 100 μL of venous blood was drawn from each of the mice and analyzed for trace element concentration. In this way we were able to study the changes in blood trace elements caused by diabetes.The results and advantages of using experimental animals, under controlled conditions, to study trace element variations caused by different diseases, are discussed in the paper.