Objective To evaluate the neurotoxic effects of intrathecal (IT) different concentrations of ethanesulfonic acid ropivacaine on spinal cord in rats. Methods Sixty healthy Wistar rats of both sexes weighing 210-220 g in which IT catheters were successfully placed according to Yaksh et al. were randomly divided into 5 groups (n= 12 each). The animals received 0.9% NaCl solution 0.4 ml (group C); 0.224%, 0.447%,0.671%, 0.894% ethanesulfonic acid ropivacaine 0.4 ml (group R1-4 ). The onset time and duration of the block were recorded. The animals were killed on 7th day after IT administration. The L4,5 segment of the spinal cord were removed for neuropathologic examination with electron microscope. The spinal cord injury was scored.Neurotoxicity was defined as the spinal cord injury score ≥ 2 and the spinal neurotoxicity was recorded. Results Onset time was shorter and duration of the block was prolonged with increasing concentrations of ethanesulfonic acid ropivacaine. The incidence of the spinal neurotoxicity was 0, 0, 17%, 42% and 100% in group C, R1, R2, R3 and R4 respectively. The incidence of the spinal neurotoxicity was gradually increased with increasing concentrations of ethanesulfonic acid ropivacaine. Conclusion IT ethanesulfonic acid ropivacaine can produce neurotoxicity to the spinal cord and it depends on the concentration.