Background: We evaluated the effect of ulinastatin on paw withdrawal threshold (PWT), IL-6, and IL-10 in SD rats after spinal nerve ligation (SNL). Methods: Group C received N/S and Group E received ulinastatin IV for three days following SNL. PWT, IL-6, and IL-10 were measured on the 3rd, 5th, and 7th day. Results: Group E showed higher PWT compared to group C. IL-6 was lower in group E than in group C. No differences in IL-10 were observed between group C and group E. Conclusion: Ulinastatin increased the PWT and its effect appears to be involved with IL-6, not IL-10.