Over a period of 5 years, 124 patients were operated on at the National Institute of Cardiology in Warsaw for acute aortic dissection, 27 of whom died. The 97 patients discharged from the hospital were included in the present analysis. The age of the patients ranged from 25 to 73 years with a mean of 50+/-10 years. Ultrasound examination of carotid arteries was performed with the patient lying on his back using a Toshiba 340A color Doppler system with a linear array probe of 7.5 MHz. Of the 97 patients examined, 15 (15%) had a dissection of at least one of the common carotid arteries (CCA). Two had Marfan syndrome. In 11 patients the dissection involved the right common carotid artery and in four it involved both the left and right common carotid arteries. The flow in the true lumen of CCA and ICA was preserved in all patients and the degree of narrowing ranged from 30 to -70%. Only one of the 15 patients with CCA dissection had an ipsilateral neurological deficit which was already present before the aortic aneurysm operation. Ultrasound follow-up was performed in all patients with the CCA dissection found on first examination. The mean duration of follow-up was 21 months. In 14 patients the degree and extent of the dissection as well as the narrowing of the true lumen was comparable, and in one patient the false channel closed spontaneously. During follow-up there were no new major neurological events despite the persistence of the CCA dissection with different degrees of narrowing of the true lumen. Doppler ultrasound examination of the carotid arteries can supply additional information about the extent of the dissection, and help to assess the flow in the persisting 'double channel' common carotid artery during the follow-up of patients.