OBJECTIVE: Postoperative delirium is a common complication in the elderly after surgery but few papers have reported after spinal surgery. We analyzed various risk factors for postoperative delirium after spine surgery. METHODS: Between May 2012 and September 2013, 70 patients over 60 years of age were examined. The patients were divided into two groups : Group A with delirium and Group B without delirium. Cognitive function was examined with the Mini-Mental State Examination-Korea (MMSE-K), Clinical Dementia Rating (CDR) and Global Deterioration Scale (GDS). Information was also obtained on the patients' education level, underlying diseases, duration of hospital stay and laboratory findings. Intraoperative assessment included Bispectral index (BIS), type of surgery or anesthesia, blood pressure, fluid balance, estimated blood loss and duration of surgery. RESULTS: Postoperative delirium developed in 17 patients. The preoperative scores for the MMSE, CDR, and GDS in Group A were 19.1+/-5.4, 0.9+/-0.6, and 3.3+/-1.1. These were significantly lower than those of Group B (25.6+/-3.4, 0.5+/-0.2, and 2.1+/-0.7) (p<0.05). BIS was lower in Group A (30.2+/-6.8 compared to 35.4+/-5.6 in group B) (p<0.05). The number of BIS <40 were 5.1+/-3.1 times in Group A, 2.5+/-2.2 times in Group B (p<0.01). In addition, longer operation time and longer hospital stay were risk factors. CONCLUSION: Precise analysis of risk factors for postoperative delirium seems to be more important in spinal surgery because the surgery is not usually expected to have an effect on brain function. Although no risk factors specific to spinal surgery were identified, the BIS may represent a valuable new intraoperative predictor of the risk of delirium.