We investigated the relationship between postoperative confusion and duration of benzodiazepine exposure, preoperative anxiety, depressive state, and cognitive function in elderly patients regularly taking benzodiazepines. We studied 328 patients ranging in age from 65 to 80 yr who underwent orthopedic surgery. Information on benzodiazepine use was obtained by face-to-face interview and visual assessment of the patient's medicine chest. Postoperative confusion was assessed by using a confusion-assessment method. The patients were divided into two groups: those who regularly took benzodiazepines and those who did not. Fifty-seven (17%) of 328 patients were treated with benzodiazepines. There were no significant differences in preoperative Mini-Mental State (MMS) scores, anxiety scores, or depression scores between benzodiazepine users and nonusers. Postoperative confusion occurred in 15 (26%) of 57 benzodiazepine users and in 34 (13%) of 271 nonusers (P < 0.01). The patients who had a score <23 on the MMS were 5 (9%) of 57 benzodiazepine users and 8 (3%) of 271 nonusers (P < 0.05). Postoperative confusion occurred in 13 (35%) of 37 long-term benzodiazepine users (daily use for >1 yr) and in 2 (10%) of 20 short-term users (daily use for <1 yr). The incidence of postoperative confusion was significantly more frequent in long-term than in short-term benzodiazepine users or nonusers of benzodiazepines. The patients who developed a score <23 on the MMS were 5 (14%) of 37 long-term benzodiazepine users and 0 (0%) of 20 short-term benzodiazepine users. In conclusion, the incidence of postoperative confusion was significantly more frequent in long-term benzodiazepine users.