Spontaneous echocardiographic contrast (SEC) is the presence of smoke-like echoes with a characteristic swirling motion of blood in echocardiography. Previous clinical studies have demonstrated that SEC is a risk factor for left atrial thrombus formation and an important indicator of potential systemic embolism originated from heart. An established relation exists between the inflammatory status and the prothrombotic state. Therefore, we investigated the role of inflammatory status on SEC in patients with mitral stenosis (MS). A total of 62 consecutive patients with MS who undergoing mitral balloon valvuloplasty were enrolled in the present study. The patients were divided into 2 groups according to the formation of SEC in the left atrium. Of the 62 patients, 32 (mean age 45 ± 12 years; 75% women) were in the SEC-negative group and 30 patients (mean age 45 ± 11 years; 63% women) were in the SEC-positive group. The high-sensitive C-reactive protein levels were significantly greater in the SEC-positive group than in the SEC-negative group (3.9 ± 2.2 vs 10.6 ± 6.3, p = 0.024). The neutrophil levels (64.6 ± 9.4 vs 72.6 ± 8.6) were significantly greater in the SEC-positive group, and the lymphocyte levels (24.4 ± 6.9 vs 18.3 ± 6.0) were significantly greater in the SEC-negative group (p = 0.001 for each). The neutrophil/lymphocyte (N/L) ratio was also significantly greater in the SEC-positive group (3.0 ± 1.8 vs 4.5 ± 1.8, p = 0.003). In the receiver operating characteristics curve analysis, a N/L ratio > 3.1 mg/dl had a 80% sensitivity and 72% specificity in predicting SEC in patients with MS. On multivariate analysis, high-sensitive C-reactive protein (odds ratio [OR] 1.235, 95% confidence interval [CI] 1.040 to 1.466; p = 0.016), N/L ratio (OR 1.461, 95% CI 0.977 to 2.184; p = 0.02), left atrial volume (OR 3.012, 95% CI 1.501 to 5.611; p = 0.001), and mitral valve area (OR 0.135, 95% CI 0.020 to 0.503; p = 0.017) were independent risk factors of SEC in patients with MS. In conclusion, the high-sensitive C-reactive protein and N/L ratio were independently associated with SEC in patients with MS.