Background: The role of microembolic signal (MES) detected by transcranial Doppler sonography in the acute phase of a stroke remains controversial in the medical literature. The prevalence of MES in the various sources of arterial brain embolism in patients in developing countries has been poorly studied. We investigated the prevalence of MES and whether MES detection is of proven use for risk stratification in the Brazilian population Methods: This was a transversal study with 45 ischemic stroke patients in acute phase at the Stroke Unit in a Brazilian hospital. All patients underwent monitoring of the middle cerebral arteries by transcranial doppler for at least 30 minutes. The examiner who conducted the monitoring was unaware of the risk stratification of the patient(single blinded). Then the record of the examination was independently analyzed by two neurologists to identify the MES. Prior to monitoring, risk stratification was carried out for all patients by complementary examinations. The independent variables were: age, NIHSS at admission, time of ictus, symptomatic carotid disease (stenosis > 60%), atrial fibrillation, intracranial stenosis, diseases of small arteries and other cardioembolic sources. The outcome was the presence or absence of MES with independent variables. The relationship between admission variables and MES was analyzed by Fisher’s Exact Test and logistic regression to estimate the odds ratio with significance defined as p<0.05. Results: The prevalence of MES was 10%. A significant correlation was found between ictus < 24 hours before transcranial Doppler examination (p=0.04; OR=5.0) and symptomatic carotid disease (p=0.03; OR=15.6) with presence of MES. There was no statistical correlation between age (p=1.0), intracranial stenosis (p=1.0), atrial fibrillation (p=0.55), diseases of small arteries (p=0.56), other cardioembolic sources (p=0.55), and the association with atrial fibrillation and symptomatic carotid disease (p=1.0). Conclusions: MES detection showed higher correlation with symptomatic carotid disease and the precocity of monitoring in relation to time of ictus too. There was no relationship found between cardioembolic source and atrial fibrillation.