OBJECTIVE: To assess causative factors that may induce the leakage of the PMMA after the vertebroplasty performed on osteoporotic compression fracture patients. METHODS: Percutaneous vertebroplasty was done on 80 vertebral compression fractures in 54 patients from June.2001 to Nov.2002. Leakage of PMMA was divided into paravertebral, venous, epidural, and intradiscal leakage. The relationship between leakage of PMMA and various factors were analyzed such as clinical features, bone mineral density, existence of bone sclerosis, interval from injury to operation, amount of PMMA, tip location, operation method, compression pattern, compression ratio etc. RESULTS: Leakage was found in 39 vertebral bodies out of a total of 80 operated vertebral bodies. A large amount of PMMA, which was injected into compressed vertebra, induced a high incidence of leakage(P=0.042). Preoperative high bone mineral density in Compressed Vertebra induced a high incidence of leakage(P=0.014). The existence of sclerosis caused a high incidence of leakage.(P=0.014). Other factors, which were examined, did not induce the leakage of PMMA. CONCLUSION: Percutaneous vertebroplasty must be done carefully after a detailed examination of factors that might cause leakage of PMMA.