A surgical operation with a "curative" aim has been performed on four patients with a lone ventricle. It consisted of a IA type in 3 cases and IC type in one. There were one operative death and three long-term survivals. The operation consisted essentially in: a delicate step of partition of the lone cavity and the treatment of the often combined, and sometimes complex, heart malformation. The trauma to the conduction pathways is one of the major dangers of this type of operation and should be avoided or decreased by the detection during operation of the His bundle. Operation should be indicated in badly tolerated forms. Stenosis of the infundibulo-pulmonary pathway interferes with the development of a hypertensive pulmonary arteriolitis, seems to be a favourable element for surgical correction. In the absence of such stenosis, one should perform a banding early enough or discuss the indication for an intracardiac operation in relation with the pulmonary artery resistance.