Disorders of intervillous circulation are covered in this sixth part of the account of Pathology of the Placenta. Proposed in this paper are a new setup and modified nomenclature in which the term of "infarction" is definitely abandoned, as there can be neither genuinely anaemic nor haemorrhagic infarction in the placenta. Alterations which we consider as a formally pathogenetic chain are discussed by the order of focus of villous collapse, reticular intervillous fibrin deposition, and chronic disorder of intervillous circulation. These should be distinguished from subchorionic fibrin deposition, a special case of chronic circulatory disorder. Reference is finally made to intervillous haemorrhage and retroplacental haemorrhage (premature detachment of the placenta). An attempt is made, in conclusion, to give an account of the causative genesis of impairment to intervillous circulation together with various pathologic-anatomic findings recordable from myometrial and decidual arteries.