A comparative study of the early clinical picture in 61 cases of internal carotid artery occlusion and 23 cases of middle cerebral artery occlusion, diagnosed by cerebral angiography and/or necropsy in patients who were either submitted to surgery or not operated upon is reported. The authors had compared the patients' age and sex, onset of the disease, ocurrence of convulsions and/or headache, onset during sleep or waking, the pre-existence of strokes, blood pressure levels, degree of consciousness, muscular strength, electroencephalography tracings, palpation and auscultation of the cervical carotid arteries. The results of the study did show that there is no statistical significative difference in these data except for 3 of them: greatest incidence of convulsions in middle cerebral artery occlusion, ophtalmodynamometry and cervical carotid symptomatology. Ophtalmodynamometry reveals significantly lower values for retinal central artery pressures on the same side as the carotid thrombosis in 70.0% of the cases, while normal and symmetrical measurements appear in all cases of middle cerebral artery occlusion. With reference to arterial signs in the neck, there were palpatory and auscultatory abnormalities in 52.4% of the patients with carotid thrombosis and in 8.6% of the cases of middle cerebral artery occlusion.