Abstract: Pessary particularly applicable in the treatment of prolapses of internal female sex organs, which pessary is formed by a ring-shaped member constructed of such material or such materials that the ring can be deformed by hand to any given shape and the circumferential dimension of the ring can be increased or decreased to some extent by hand, after which the ring retains the ultimately given shape and circumferential dimension. Preferably the ring (1) consists of a core (4) which has the shape of a spiral of non-resilient nature and a flexible casing (5) enclosing said core (4).