In 99 of 2250 consecutive C.B.P. cases, signs of cerebro-vascular disease (C.V.D.) were recorded in 87 (3.9%) on admission and in 12 post-operatively. The detection of C.V.D. by auscultation alone is very incomplete. There were 17 post-C.B.P. neurologic deficits (P.O.N.D.) (0.75%): 15 strokes (0.67%) and 2 T.I.A.'s. 26 patients (out of 87 detected on admission) were treated by carotid endarterectomy (C.E.) either pre-by-pass or simultaneously. There were no complications. The remaining 61 patients, who were not treated, had 4 strokes and 1 T.I.A. after their C.B.P. The most probable cause of these deficits was pre-existing C.V.D. Could more extensive pre-operative investigation, and treating the serious lesions by C.E., improve the P.O.N.D. incidence? The published series on simultaneous C.E. + C.B.P. are not yet conclusive. We favour C.E. done before the C.P.B. procedure except in very serious coronary disease when simultaneous operation is preferred.