We investigated the relationship between left atrial spontaneous echo contrast (SEC) and cerebrovascular features in nonvalvular atrial fibrillation (NVAF). Few reports have been published to compare cardiac and cerebrovascular imaging in patients with NVAF. Forty-four patients with NVAF were studied using transesophageal echocardiography and non-invasive imaging including magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and transcranial color Doppler imaging (TCD) in the middle cerebral artery (MCA) territory. The symptomatic severity was divided into asymptomatic, transient ischemic attack (TIA), and stroke. The severity of the MRI findings was divided into normal, small, and large infarcts. The severity of the MRA findings was divided into normal, attenuation, and occlusion. MCA was bilaterally scanned and a side-to-side asymmetry ratio of pulsatility index (PI) was measured. The severity of SEC was divided into normal, SEC, and thrombi. Five patients with other thromboembolic risk or poor results of TCD were excluded. SEC and thrombi were detected in 12 (30%) and in 3 patients (5%), respectively. TIA and stroke were detected in 8 (21%) and in 17 patients (44%), respectively. Small and large infarcts were detected in 9 (23%) and in 18 patients (46%), respectively, on MRI. Attenuation and occlusion were detected in 14 (36%) and in 8 patients (21%), respectively, on MRA. PI ratio was 1.21 +/- 0.25. SEC severity was highly associated with PI ratio and MRA severity in monovariate analysis (P < 0.005), P < 0.01, respectively). SEC severity was highly associated with PI ratio and MRA severity in stepwise multiple regression analysis (P = 0.0001, r = 0.630, n = 39). In patients with NVAF, left atrial SEC was highly related to attenuation or occlusion on MRA and imbalance of cerebral blood flow on TCD in the MCA territory.