OBJECTIVE The aim of our study was to assess the influence of previous contralateral carotid endarterectomy (CEA) and of the timing of the procedures on cerebral clamping ischemia during the second operation in patients undergoing staged bilateral CEA. METHODS We reviewed the 251 patients who presented with bilateral carotid stenosis of > or =70% at the time of the first admission and underwent staged bilateral CEA between January 2001 and December 2004. Surgery was performed under locoregional anesthesia. Cerebral perfusion was monitored with mental status and contralateral motor function evaluation in awake patients. Selective carotid shunting was performed for patients who manifested neurologic deficits. Univariate and multivariate analyses were performed for the variables of interest. RESULTS Twenty-two patients (8.8%) required carotid shunting during the first procedure and 28 (11.1%) during the second one. Nine of the latter also had shunts during the first CEA, whereas 19 tolerated cross-clamping during the first operation. Among the patients who underwent contralateral CEA < or =30 days, 23 of 146 required carotid shunting; between 31 and 60 days, 4 of 73; and after 61 days, 1 of 32 (P = .023; univariate analysis). The chi2 for trend was statistically significant (P = .009). Patients operated on the second side < or =30 days had a nearly fourfold risk of shunting during the second procedure compared with patients operated on > or =31 days. The highest risk was observed in patients with a shunt during the first operation who underwent the second CEA < or =30 days. Multivariate analysis also identified the time intervals between CEAs and the need of shunting during the first procedure as independent risk factors (P = .042 and P < .001). CONCLUSIONS These data show an increased incidence of cerebral clamping ischemia during contralateral endarterectomy performed < or =30 days; whereas after longer intervals between CEAs, the need for shunting is significantly reduced.