This study is devoted to a series of 30 anatomical cases of mitral atresia. The left atrium was dilated in 5 cases and hypoplastic in 25. The interatrial ostium was small in 50% of the hearts. Left atrio-ventricular concordance was present in 29 cases, as against 1 case of discordance. There was no atrio-ventricular connection in 29 cases, and the mitral valve was imperforate in 1 case. Connections between the tricuspid valve and the main ventricle were normal in 26 hearts. The tricuspid valve straddled the septum in 4 cases. Five hearts had two ventricles, 25 had a single ventricle. Nine hearts showed no ventriculo-atrial atresia. The main vessels were normally located in 1 case, transposed in 2 and originated in the right ventricle in 2 cases; in the 5 hearts with single ventricle the two main vessels arose from the main cavity. Seventeen hearts had an atresic aortic valve and a hypoplastic ascending aorta; the pulmonary artery arose from the right ventricle in 1 case and from the main chamber of a single ventricle heart in 15 cases. The pulmonary valve was atresic and the aorta arose from the main chamber of a single ventricle heart in 4 cases.