Injection of India ink and clipping are relatively well-known methods for marking lesions of the gastrointestinal tract. The use of metal clips provides a radiologically recognizable mark, which is also palpable at surgery. In addition, clips can be extremely useful as landmarks in comparing endoscopic findings with the resected specimen. Previous reports of clip-marking have concentrated on the Olympus (Tokyo, Japan) HX-2L clip, but this clip has the disadvantages of having too wide a diameter to be used through most conventional endoscopes and also a relatively low clip-retention rate, as the depth of its bite is limited. Recently, Olympus has marketed a new clip (HX-3L) designed by the author for hemostasis in cases of gastrointestinal bleeding. This new clip is an improved version of the cassette-type J-clip that was previously reported by the author in this journal. The prime advantage of the HX-3L is that the endoscopist can use it via a panendoscope without any assistance. In addition, it has an excellent bite and a very high level of safety. In terms of function and application, it is completely different from the HX-2L. In addition, the tip (the portion that actually grasps tissue) of the HX-3L is longer and thinner than the HX-2L, thus permitting a firm grasp of the muscularis mucosae layer even when approaching from an upper oblique angle and this, in turn, improves the performance of the clip as a marker.(ABSTRACT TRUNCATED AT 250 WORDS)