A case is reported in which the entire pulmonary venous return was abnormal, being retro-cardiac. Unusual features were the age at which the abnormality was discovered (14 years), and the anatomical type of abnormality of pulmonary venous return. The return effectively emptied into a posterior cavity which was "a diverticulum of the right atrium" which had a wide communication with the "normal" right atrium, which in turn communicated with the left atrium by a highly placed Ostium Secundum. The muscular septum which separated the highly placed auricle of the left atrium and the "diverticulum" was removed, and vertical partitioning allowed a right and left atrial cavity to be reconstituted. The post-operative progress was uneventful.