Abstract: The invention relates to a device (1) for access to preformed body cavities, such as thoracic drains, in particular for arthroscopy or laparoscopy on the human or animal body, comprising a base (3), a shaft (4) guided in the base (3), which shaft is designed to be longer than the base (3), and a cutting instrument (5), which is arranged in the shaft (4) and is guidable therein and which upon forward movement carries the shaft (4) as far as a predetermined position beyond the base (3). A device (1) according to the invention is characterised by ease of use, in particular for inexperienced surgeons, and the opportunity for rapid implementation of an arthroscopic procedure by means of a minimally invasive intervention in the body.