The aim of this study was to determine optimal protective thiopental dose in renal ischemia/reperfusion (I/R) damage. This study was carried out on 42 rats. After abdominal midline incision, left renal artery was occluded. After 60 min of ischemia and reperfusion, a left nephrectomy was performed. Surgical intervention was made for the six rat groups (excluding sham group). In control group, 60 minutes of ischemia and reperfusion were applied to left kidneys. Thiopental (3, 10, 30, 60, 80 mg/kg) was applied intra-peritoneally to the rats except sham and control groups 15 minutes before reperfusion. After reperfusion, IL-1 alpha, IL-6, TNF-alpha levels; SOD activity; MDA and NO levels were measured. There was no decrease in IL-6 or TNF-alpha levels in groups at all doses. IL-1 alpha levels only decreased in the group receiving 3 mg/kg thiopental. Only the group receiving 80 mg/kg observed decrease in MDA levels. The rats receiving 30 mg/kg showed significant increase in SOD levels. The rats receiving 3 mg/ kg detected significant increase in glutathione peroxidase (GPx) levels. The groups receiving 10, 30, and 60 mg/kg thiopental showed decrease in nitric oxide (NO) levels. According to study results, different doses of thiopental affected each biochemical indicator in renal I/R damage.