OBJECTIVE: To investigate the effects of nerve root compression on dorsal root ganglia. METHODS: Following the method of Kawakami, 4/0 ribbon gut were applied around left L4-6 spinal nerve roots in 50 SD rats. Just 3 mm cranial to the dorsal root ganglia, the nerve roots were secured by two ligation node. The nerve roots of right side were as control. The L4-6 spinal cord was taken out 1, 2, 4, 8, 12 weeks after surgery, respectively. The activity of fluoride resistant acid phosphatase (FRAP) was determined by the enzyme histochemistry (Gomori method) and the image analysis technique. RESULTS: In the test side, the FRAP content of spinal dorsal horn reduced 4 weeks after operation. And there were gradually more and more decreases from 4 to 12 weeks. There was significant difference between the test side and control side (P lt; 0.01). CONCLUSION: Chronic nerve root compression causes damage to dorsal root ganglia.