Clinical and pathologic data were reviewed in 20 patients who had have surgery for isolated aortic valvular heart disease between April 1978 and April, 1987. Hospital mortality was 10%, with no additional late mortality during a mean follow-up period of 24.1 months. Prosthetic valve failure developed in 3 patients and two had reoperation. Niety four percent of the survivors who were in NYHA Funtional class III or IV before operation are now in class I or II. Ninety percent of all patients are still alive at a maximum follow up of 9 years. The clinical histories, gross and histologic examination of valves estabilished the causes for isolated aortic valve disease: 3 rheumatic, 2 congenital bicuspid, 2 hypertention, 2 aortitis and each one case of floppy valve, medial cystic necrosis of aorta, bacterial endocarditis. But etiology was unknown in 8 cases. Sixteen patietns had myxoid degeneration, defined as significant disruption of the valve fibrosa and its replacement by acid mucosaccharides and cystic changes. Myxoid degeneration was also the primary pathologic abnormality in the patients with 2 hypertention, 2 rheumatic, 1 aortitis, 1 bacterial endocarditis, 1 floppy valve, 1 congenital bicuspid. The patients with myxoid degeneration of uncertain origin were 8. Histologic finding of all of them revealed nonspecific patients with myxoid degeneration of uncertain orgin were 8. Histologic finding of all of them revealed nonspecific chronic valvulitis with myxoid degeneration. This finding may indicate that the etiology w uld be infectious.