Abstract: Apparatus for enabling the use of a computer mouse at a sterile surgical site comprises a pouch for the accommodation of the mouse and an inlet sleeve forming an inlet passage into the pouch. The pouch and sleeve are formed of pliable, preferably transparent sterilizable material. When the mouse has been admitted to the pouch via the passage, the sleeve may be separated from the pouch and the open mouth of the latter rolled to form a seal, thereby retaining the mouse within the pouch.