In a study of 136 tapping of ovarien cysts carried out in the surgical departement of Broca Hospital from 1968 to 1971, the authors point out the diagnostic interest of such a practice, which is harmeless if the contra-indications are respected and often easily carried out (tapping needle by Mintz). The macroscopic and cytological aspect of the liquid tapped enable one to make a precise diagnostic in almost all cases and to lead the therapy in the proper direction.