An anoscope (1) comprises: a fixed portion (2) that is hollow and open at the opposite ends； a mobile portion (3) that is hollow and open at the opposite ends, which is shapingly coupled with said fixed portion (2) and is arranged for rotating coaxially inside said fixed portion (2)； a window (8) that is obtained in said mobile portion (3) and is arranged for making accessible a portion of rectal mucosa； a dilator (4) that can be alternatively inserted in, or extracted from, a longitudinal cavity (13) of said anoscope (1), said longitudinal cavity (13) being comprised in said mobile portion (3). The anoscope (1) is characterized in that it comprises positioning and locking means (9) arranged for preventing said mobile portion (3) from rotating coaxially inside said fixed portion (2) when said dilator (4) is not inserted in said longitudinal cavity (13).
