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Aim: The use of low frequency probes allows to overcome the resistance of the skull and evaluate Willis's circle by B-mode and Trans-Cranial Color-Doppler (TCCD) to obtain morphological and functional information related to brain circulation during pathologic conditions. With the new software available today modern technology allow us to measure the transient scattering produced by the rupture of the contrast medium microbubbles and estimate the presence of the contrast medium both in macro- and microcircle. In this way it is possible to appraise parenchymal perfusion. This study aims to assess the intracranial micro- and macrocircle using TCCD with contrast medium (Levovist) and to compare the results with the patients' clinical signs., Material and Methods: We studied 21 subjects aged 45-73 years (mean 68 years) with atheromatous uncomplicated plaques in the internal carotid artery producing varying degrees of stenosis and 10 healthy controls. The examinations were performed using an ATL HDI 3000 ultrasound machine with a Phased Array 3.25 MHz probe. The mechanic index was calibrated to high values to obtain rupture of the microbubbles under insonation. Intensity/time curves of transient scattering were extrapolated for both the cerebral macrocircle and the parenchymal microcircle in the region of interest., Results: The curves were compared with the clinical presentation of the different classes of patients and the results obtained were consistent in showing a clinical pattern of perfusional deficit in subjects with symptoms of chronic brain ischemia. In particular, it was possible to compare the morphologic data relative to the contrast medium decay curves with the patient's clinical condition, confirming the suspicion of cerebral microcircle pathology., Conclusion: Thanks to improvements in the software and to the definition of effective algorithms, contrast-enhanced TCCD will be able to provide information on brain perfusion in a simple, inexpensive and relatively non-invasive manner.