Quantum dots are new types of fluorescent materials for biological labeling. As a result, QDs toxicity study is an essential requirement for future clinical applications. Therefore, the cytotoxic CdSe:ZnS quantum dots effects on some organs in mice are presented in this study. In this work, 10, 20 and 40 mg/kg doses of CdSe:ZnS quantum dots were injected to 32 adult male mice. Structural and optical properties of quantum dots were studied by XRD. The testis and liver weight of various groups were analyzed using SPSS 16 program (one way ANOVA test) and histological changes in testis, liver tissues were analyzed by Light microscopy. Testis tissue showed high toxic effect in 40 mg/kg dose. Also histological study of liver tissue showed degeneration of hepatocyte cytoplasm, nuclear matters and sinusoidal dilation in dose-dependent manner in comparable to control groups but the lobular architecture is largely maintained in10, 20 and 40 mg/kg doses. The body weight did not change significantly in any of the CdSe:ZnS treated groups. The testis weight (TW) decreased significantly in mice that received 40 mg/kg CdSe:ZnS QDs and liver weight in the case of mice treated with 20, 40 mg/kg CdSe:ZnS QDs were increased significantly. According to the differences the toxicity of quantum dot on testis and liver tissues in adult, it seems that various organs have different responses to quantum dots toxicity. پرونده مقاله