Abstract: To explore the influence of blood glucose level on 18FFDG uptake in tumor and normal tissues of mice, thirtyfive mice carrying Ehrlich ascitic cancer (EAC) are fasted 20 h and divided into four groups. The glucose loading group (n=12) and the control group (n=11) is given a solution of 50% glucose and distilled water orally just one hour before the 18FFDG injection. Another two groups (n=5, n=7) is given a solution of 10%, 30% glucose respectively. Before 18FFDG intravenous injection, blood glucose levels are measured. The mice are killed one hour after the 18FFDG injection. The tumor and normal tissues are excised, weighed, and counted by a γ well counter. The quantity of 18FFDG uptake is expressed as standardized uptake value (SUV). Blood glucose levels of the mice with EAC in the glucoseloading group are significantly elevated than the control group (11.98±3.01 mmol/L vs. 3.95±1.11 mmol/L, P<0.01). The SUVs of tumor, brain, spleen, blood and the 18FFDG uptake ratios of tumor and muscle in the glucoseloading group (1.34, 0.86, 0.48, 0.09, 1.38 respectively) are significantly lower than those in the control group (3.02, 2.62, 0.80, 0.16, 5.38 respectively) (P<0.01). The SUVs of heart and muscle, the 18FFDG uptake ratios of tumor and brain, heart and blood in the glucoseloading group (8.31, 1.05, 1.58, 103.00 respectively) are significantly higher than those in the control group (1.57, 0.64, 1.20, 9.73 respectively) (P<0.01). There are no difference betweene the two groups in the SUV of lung, liver and kidney, and in the tumor SUVc. The correlation of tumor, brain, spleen and blood SUVs and the uptake ratios of tumor and muscle with blood glucose levels are negative, and the correlation coefficients are -0.76, -0.92, -0.78, -0.48 and -0.63, respectively (P<0.01). The correlation of heart, muscle SUVs, the uptake of ratios of tumor and brain, heart and blood, and the tumor SUVc (corrected with blood glucose) with blood glucose levels are positive, the correlation coefficients are 0.85, 0.43, 0.51, 0.85 and 0.45, respectively (P<0.01). The results show that the blood glucose level significantly affects the 18FFDG distribution in mice, suggesting the blood glucose level should be controlled during clinically 18FFDG imaging.