Thirty patients with endomyocardial fibrosis were submitted to endocardial decortication and atrioventricular valve replacement between December, 1977, and October, 1981. There were 26 female and four male patients, ranging in age from 14 to 48 years (mean 32). Thirteen patients had biventricular disease, 14 had the right-sided form, and three had endomyocardial fibrosis confined to the left ventricle. All were in Functional Class III or IV (New York Heart Association classification). The hospital mortality was 20% (six cases). Among the survivors (mean follow-up 13 months), 23 of 24 were improved clinically. Postoperative hemodynamic and angiographic studies were performed in 15 patients. Two (6.6%) have definitive atrioventricular heart block. There were five (16.6%) late deaths. Operation for endomyocardial fibrosis should be considered a palliative procedure. Possible limitations include the need for a valve prosthesis, cardiac conduction disturbances secondary to endocardiectomy of the right ventricle, and the possibility of recurrence of the endocardial fibrosis. However, at present, operation seems to be the treatment of choice for this condition because (1) endomyocardial fibrosis is characterized by a grave prognosis and medical therapy is ineffective; (2) endomyocardial fibrosis is a disease in which only the heart is affected, lesions in other organs being the result of passive congestion; (3) systolic performance of the heart is usually only slightly depressed; and (4) the surgical procedure is easily performed, so that the mortality is acceptable.