Objective: To assess the frequency of mitral stenosis and its severity in adult patients of rheumatic valvular heart disease. Methodology: A cross sectional and retrospective study was conducted in medical department of LUMHS Hyderabad and MMC Mirpurkhas hospitals, from Sep 2005 to June 2011. 200 adult patients of rheumatic heart disease were randomly included in this study. Diagnostic criteria for acute rheumatic fever used were revised Jon's criteria. Record files of patients were collected and studied thoroughly. Special proforma were prepared. Diagnosis was confirmed by ECG, X-Ray chest, transthoracic two dimensional 2D echocardiography and Doppler studies. Severity of mitral stenosis was graded by 2D echocardiography, using planimetry and Doppler. By Doppler technique the severity of mitral stenosis was assessed by atrioventricular (AV) pressure half-time. By typical CW continuous wave spectral recording of mitral stenosis, mitral valve gradient; end- diastolic pressure gradient and mean pressure gradient were calculated using the modified Bernoulli equation to assess the severity of mitral stenosis. Statistics: Statistical analysis was carried out by SPSS 16. Percentages mean values, standard deviation, variance in standard deviation and p value was calculated. Results: Age of patients was from 12-70 years, mean age was 35.21 ± 19.75 years and median age was 31 years. Males in our study were 88 (44%) and females were 112 (56%). Male/Female ratio was 1/1.3. 124 (62%) patients were between 12-30 years and 76 (38%) patients were above 30 years. Mitral stenosis was seen in 66 (33%) patients. Next most common cardiac lesion in our study was mitral regurgitation 56 (28%). Mixed aortic valve disease was 24 (12%). Aortic stenosis was in 10 (5%) and 130 (65%) had various grades of pulmonary hypertension Table 1. Severity of mitral stenosis was assessed by different techniques. Frequency of severe MS has been shown in Table 2. Mean values are shown in Table 3. Conclusion: It has been concluded in this study that in adult patients with rheumatic heart disease, the frequency of mitral stenosis was 66 (33%). Severe MS was 15(22.7%) by end- diastolic pressure gradient method and 18 (27.3%) by planimetry. Severity calculated by various techniques was similar.