STUDY DESIGN: A retrospective study of perioperative complications was performed in elderly patients undergoing posterior decompression and fusion for lumbar degenerative conditions. OBJECTIVES: To identify the perioperative complications and to analyze the influence of posterior decompression and fusion on the occurrence of the morbidity. SUMMARY OF BACKGROUND DATA: Because of the better long-term results, the decompression and fusion with instrumentation have been recently recommended for treatment of degenerative lumbar disease in the elderly. However, the perioperative complication rate and their correlating factors have not been adequately defined. MATERIALS AND METHODS: A retrospective review of the medical charts of fifty-one patients aged 65 years or older operated during June 1997 to July 1998 was undertaken. The minimum follow-up required for inclusion was three months. All medical and surgical perioperative complications directly related to the surgical procedure were noted. The association of fusion levels and other factors with the occurrence of perioperative complications were analyzed. RESULTS: Perioperative complications occurred in 17(33.3%) of the 51 patients. Seven patients(13.7%) had at least one major complication, 5(9.8%) had at least one minor complication and 9(17.6%) had insignificant complications. Hematoma and wound infection were the most common surgical complications. Paralytic ileus was the most common medical complication. There was no difference in the rate of perioperative complications between the long and short fusion groups. An age of more than seventy-five years at the time of surgery was associated with a higher risk of complications. There was no statistically significant relationship between the perioperative complications and sex diagnosis, operative time, type of bone grafting, amount of blood transfusion, or preoperative comorbidity of the patients. CONCLUSION: Perioperative complications were quite common in the present series, occurring in 33.3% of the patients. An age over seventy-five years was a risk factor for associated with morbidity. The number of levels fused and the comorbidity did not associated the development of the complications.