Herein described is an instrument guide for use with a colonoscope, the guide being adapted to be mounted to the colonoscope. The guide defines a channel along which an instrument can be passed during use. Also described is a method of removing a polyp from a colon including inserting a colonoscope into the colon, inserting an instrument guide into the colon, mounting the guide to the colonoscope, inserting an excision instrument, excising a polyp and withdrawing the excised polyp from the colon.
