Objective To evaluate the effect of stellate ganglion block (SGB) on cellular immune function in diabetic rats. Methods Healthy male Sprague-Dawley rats, aged 3 months, weighing 240-280 g, were used in this study.Diabetes mellitus was induced by intraperitoneal 1% streptozotocin 60 mg/kg and confirmed by blood glucose ≥16.7 mmol/L 3 days later.Forty-eight rats with diabetes mellitus were randomly divided into 2 groups (n=24 each) using a random number table: diabetes mellitus group (group DM) and group SGB.Another 24 healthy rats, aged 3 months, were selected and served as control group (group C). At 1 week after successful establishment of the model, unilateral transection of cervical sympathetic trunk (TCST) was performed in group SGB, while the right cervical sympathetic trunk was only exposed in C and DM groups.Before TCST (T0) and on 1, 3, 7 days after TCST (T1-3), 6 rats were randomly selected from each group, and blood samples were collected from the inferior vena cava for determination of the blood glucose, plasma norepinephrine (NE) concentrations (by enzyme-linked immunosorbent assay), and levels of T lymphocyte subsets CD3+ , CD4+ and CD8+ in whole blood (using FACSCalibur flow cytometer). CD4+ /CD8+ ratio was calculated.The rats were weighed before sacrifice, and the rats were sacrificed to obtain the thymus which was weighed.The thymus index (thymus weight/body weight) was calculated. Results Compared with group C, the blood glucose was significantly increased, and the levels of CD3+ and CD4+ in whole blood, CD4+ /CD8+ ratio, and thymus index were significantly decreased at T0-3 (P 0.05), the plasma NE concentrations were significantly decreased at T1-3 in group SGB (P 0.05). Compared with group DM, the blood glucose and plasma NE concentrations were significantly decreased, and the levels of CD3+ and CD4+ in whole blood, CD4+ /CD8+ ratio, and thymus index were significantly increased at T1-3 (P 0.05). Conclusion SGB can improve the cellular immune function in diabetic rats. Key words: Stellate ganglia; Nerve block; Diabetes mellitus; Immunity, cellular