Over the last three decades there has been a world-wide decline in the incidence and severity of rheumatic fever and rheumatic heart disease, but the death rate in Singapore from chronic rheumatic heart disease has risen from 3.6 per 100,000 population in 1966 to 4.4 per 100,000 in 1977. Valvular lesions from rheumatic heart disease are very common, and between 1967 to 1979, 715 surgical procedures were performed for rheumatic valvular disease, and of these, 654 procedures involved the mitral valve which was most commonly affected by the disease process. Since many of the patients were female and in the child-bearing age, conservative procedures on the mitral valve were performed whenever possible. Mitral valvotomy for mitral stenosis relieved symptoms effectively; and for restenosis of the mitral valve, more than half of the patients underwent a second valvotomy with functional improvement. Mitral valve replacement was reserved for the severely distorted valve, sometimes calcified, and where there was stenosis associated with incompetence. Between 1971 to 1979, 162 mitral valves were replaced and actuarial studies showed 80% survival five years after surgery. 30 aortic and mitral valve replacements were performed in this same period with an operative mortality of 16.7%. Only 75 aortic valves were replaced for rheumatic valvular disease and 14 of these also had associated mitral and triscuspid valve disease. The prosthetic valves commonly used for replacement were the Starr-Edwards non-cloth covered valves, models 6120 and 1260. All patients that had valve replacements were treated with long-term anticoagulation with Warfarin. The incidence of thromboembolism was low, being 8% for mitral valve replacement and the majority of these episodes occurred in the first three months after surgery.