Background: Delayed recovery of cognitive function is a well-recognized phenomenon in older patients. The potential for the volatile anaesthetic used to contribute to alterations in postoperative cognitive function in older patients following minor surgical procedures has not been determined. We compared emergence from isoflurane and sevoflurane anaesthesia in older surgical patients undergoing urological procedures of short duration. Methods: Seventy-one patients, 60 yr of age or older, undergoing anaesthesia expected to last less than 60 min for ambulatory surgery, were randomly assigned to receive isoflurane or sevoflurane. A standardized anaesthetic protocol was used, with intravenous fentanyl 1 mu g kg(-1) and propofol 1.5-2.0 mgkg(-1) administered to induce anaesthesia. Anaesthesia was maintained with either sevoflurane or isoflurane in 651% nitrous oxide and oxygen. Early and intermediate recovery times were recorded. The mini mental state examination and digit repetition forwards and backwards were administered at baseline, and at 1, 3 and 6 h postoperatively, to assess cognitive function. Results: There were no between-group differences in (sevoflurane vs. isoflurane, mean +/- standard error of the mean) times to removal of the laryngeal mask airway (7.7 +/- 0.6 vs. 7.1 +/- 0.4 min), verbal response time (10.1 +/- 0.7 vs. 9.9 +/- 0.7 min) and orientation (12.1 +/- 0.7 vs. 12.1 +/- 0.7 min). Intermediate recovery, as measured by time to readiness for discharge from the post anaesthesia care unit (44.9 +/- 1.5 vs. 44.3 +/- 1.5 min), was similar in the two groups. Postoperative indices of cognitive function and attention were comparably reduced at I h, but returned to baseline in both groups at 6 h. Conclusions: Isoflurane and sevoflurane anaesthesia resulted in similar clinical and neurocognitive recovery profiles in older patients undergoing ambulatory surgical procedures of short duration.