Background and Aims: We developed a through-the-scope twin clip (TTS-TC) for closing GI wounds. The objective of this study was to evaluate the efficacy and safety of the TTS-TC in GI wound closure.Methods: GI nonperforating and perforating wounds (!2.5 cm) were created in live pigs. TTS-TCs were used to convert the large wounds into small wounds. The remaining small wounds were closed using conventional throughthe-scope clips (TTSCs). The follow-up period was 1 month. Location and size of the wound, time of wound closure, intraoperative and postoperative adverse events, and conditions of wound healing were investigated.Results: Thirteen wounds were created in 5 live pigs, including 2 gastric nonperforating and 3 perforating wounds and 5 large intestinal nonperforating and 3 perforating wounds. The mean long and short diameters of the wounds were 4.1 (AE .9) cm and 3.4 (AE .7) cm, respectively. All wounds were successfully closed using the TTS-TCs combined with TTSCs. The total mean time for wound closure was 9.2 (AE 5.3) minutes, and the mean time for using the TTS-TCs was 3.9 (AE 4.7) minutes. During the 1-month follow-up period, no bleeding, perforation, or death occurred; all wounds healed with scar formation; and all TTS-TCs detached spontaneously. Conclusions:The TTS-TC was successfully used to close large-sized GI wounds. The TTS-TC is a promising tool for large-size wound closure under flexible endoscopy.Minimally invasive surgeries, such as endoscopic submucosal dissection (ESD), endoscopic full-thickness resection (EFR), and natural orifice transluminal endoscopic surgery, are extensively used for treating GI diseases. A recent study also showed that wound closure after ESD might be useful in preventing delayed bleeding and perfo-ration. 1 Thus, wound closure is a common but challenging problem in these minimally invasive surgeries. [2][3][4] Firm and rapid closure of wounds plays an important role in patient prognosis, especially for perforating wounds. Currently, the main instruments 3-7 for wound closure while using a flexible endoscope are conventional through-the-scope Abbreviations: EFR, endoscopic full-thickness resection; ESD, endoscopic submucosal dissection; OTSC, over-the-scope clip; TTSC, through-thescope clip; TTS-TC, through-the-scope twin clip.