127 patients with diagnosis of acquired mitral and aortic valve disease confirmed by cardiac catheterization were followed for 5-17 years (mean 10 years) under conservative management. At the end of the study, 80 patients were still alive, and 68 of them were examined again. 23 patients died, and no information was available on 24. Analysis of the natural course of the disease showed that results obtained with different classification systems (NYHA, clinical findings, hemodynamic data) were not comparable. However, the majority of mitral and combined mitral-aortic lesions remained stable over the years, independent on the initial classification of the lesion. Aortic valve disease became hemodynamically worse in the absence of subjective and clinical change.