BACKGROUND: Endocardial fibroelastosis (EFE) is a diffuse thickening of the ventricular endocardium resulting from proliferation of fibrous and elastic tissue. Primary and secondary forms have been described. Primary EFE occurs in the dilated and contracted forms. EFE usually manifests as unexplained congestive heart failure in infants younger than 1 year old. OBJECTIVES: To analyze the epidemiologic, clinical and anatomopathological aspects of primary EFE. METHODS: Eleven cases of histologically confirmed EFE were found in 6211 necropsies performed between 1960 and 2000 in the Hospital of the University of Paraná. Results: In nine cases (81.8%) the initial clinical presentation occurred before the age of 1 year. In eight cases (72.7%) patients died before the age of 1 year. The most common clinical findings were tachypnea (54.5%), hepatomegaly (45.5%), cough (36.4%) and fever (36.4%). Cardiomegaly was the main radiographic finding, present in all cases (n = 6). The endocardial thickening was more frequent at the left heart (90.9%). The death cause was acute respiratory failure in five cases (45.5%) and cardiogenic chock in four cases (36.4%). DISCUSSION AND CONCLUSIONS: The results showed that EFE affects usually infants younger than 1 year old that rapidly progress to death. Some common clinical findings like tachypnea, cough and fever suggested respiratory infection which was confirmed by necropsy in three cases (27.3%). The complementary tests showed only non-specific findings of congestive heart failure. The information analyzed here demonstrated no significant difference of the epidemiological, clinical and anatomopathological characteristics of primary EFE between Brazil and the international literature.