BACKGROUND: Rheumatic heart disease remains the most common cardiovascular disease in children and young adults. The outcome of interventional versus medical therapy on the long term is not fully elucidated yet. This study provides contemporary data on the clinical profile, treatment and follow up of patients with rheumatic mitral stenosis (MS) in Tanzania. METHODS: Patients' medical information, investigations and treatment data were recorded in this prospective cohort study. They were followed up for 6-24 months to determine the long-term outcome. Interventional therapy was defined as a combination of surgery and percutaneous balloon mitral valvuloplasty. Kaplan-Meier curves and Cox proportional hazards model were used in analyses. p-Value < 0.05 was considered statistically significant. RESULTS: We enrolled 290 consecutive patients. Interventions were done in half of the patients. Median follow up was 23.5 months. Mortality was higher in the medical than interventional treatment (10.4% vs. 4%, log-rank p = 0.001). Median age was 36 years, females (68.3%) and low income (55.5%). Multivalvular disease was found in 116 (40%) patients, atrial fibrillation (31.4%), stroke/transient ischaemic attack (18.9%) and heart failure class III-IV (44.1%). Median (IQR) duration of disease was 3 (4) years, secondary prophylaxis (27.7%) and oral anticoagulants use (62.3%). In multivariable analysis, the risk of death among patients on medical was 3.07 times higher than those on interventional treatment (crude HR 3.07, 95% CI 1.43-6.56, p = 0.004), 2.44 times higher among patients with arrhythmias versus without arrhythmias (crude HR 2.44, 95% CI 1.19-4.49, p = 0.015) and 2.13 times higher among patients with multivalvular than single valve disease (crude HR 2.13, 95% CI 1.09-4.16, p = 0.026). CONCLUSIONS: Intervention is carrying low mortality compared to medical treatment. Arrhythmias and multivalvular disease are associated with a high mortality. Rheumatic MS is more prevalent in young people, females and individuals with low income. There is a late hospital presentation and a low use of both secondary prophylactic antibiotics and anticoagulants.