The value of prosthetic valve replacement is determined not only by the improvement in life expectancy but also by the quality of life. This statement resulted from an analysis of 168 patients undergoing isolated aortic -- or mitral -- valve replacement between 1970 and 1976. Besides numerous complications -- probably often avoidable such as side effects of incorrect anticoagulation -- long term results of 125 surviving patients were satisfactory over a period of 3-9 years after surgery. Though complete restitution was rare, subjective and objective improvement -- different and dependent on type and degree of valve disease -- was persisting and the effect on social and professional incorporation surprisingly positive.