Abstract: Progressive Surgical Distraction Device (PSDD) intended for enabling gradual atraumatic access to cavities and zones inside the human body and for allowing controlled extraction of the liquids contained therein, particularly open foetal surgery and neurosurgery. It is composed of a set of cylindrical and semi-cylindrical parts of increasing diameters and decreasing lengths that fit into each other telescopically, each enabling the successive extraction of the inner part. The progressive distraction of the muscular fibres does not subject them to traction, avoids haemorrhages and allows the controlled diversion of liquids without accumulation of residues. The last part of the sequence is designed to allow an optimum mobilisation of the clamping system via directly viewed control of the intervention zone and surgical field.