BACKGROUND: Aspartame, as a synthetic sweetener, has been widely used in food products during the recent decades and renal excretion of aspartame lasts several days. OBJECTIVES: The aim of the present study was to investigate the dose-dependent effects of aspartame on morphometrical and histometrical changes of the kidney in immature mice. METHODS: 24 immature female Balb/C mice, were randomly categorized to three experi-mental and one control groups of 6 mice each. Experimental and control groups received aspartame100, 200 and 400 mg/kg/bw respectively and distilled water with the same method for 21 days. At the end of the experiment, the mice were weighed and anesthetized their right kidneys were stained with Hematoxylin and Eosin. RESULTS: body weight difference showed significant decrease in experimental groups of 100, 200, 400 mg/kg/bw (1.43±0.198, 1.64± 0.281, 2.60±0.388) respectively compare to the control groups (4.65±0.139), length, width, diameter and weight of kidneys had significant decrease between experimental and control groups(p<0.05). In the case of histometrical changes, the diameter of glomeruli, diameter of renal corpuscles and the height of epithelium of proximal and distal convoluted tubules showed significant decrease in experimental groups compared to control group (p<0.05). The diameter of urinary space and lumen of proximal and distal convoluted tubules, experimental groups showed significant increase compared to control group (p<0.05). CONCLUSIONS: This can be concluded that aspartame can induce morphometrical and histometrical changes in mice kidney.