OBJECTIVE. Although endoscopic treatment for early gastric cancer (EGC) is an accepted therapy in South Korea and Japan, long-term outcomes remain unknown. We evaluated the clinical outcome of endoscopic submucosal dissection (ESD) for gastric dysplasia and EGC. MATERIAL AND METHODS. A total of 402 patients with gastric dysplasia and EGC were treated with ESD at a single hospital from January 2004 to December 2007. The patients underwent ESD and then received periodic endoscopic follow-up and metastatic surveys for 9-49 months (median 30 months). Resectability (en bloc or piecemeal resection), curability (complete or incomplete), local recurrence, and disease-free survival rates were estimated. RESULTS. There were 107 patients with low-grade dysplasia (LGD), 97 with high-grade dysplasia (HGD) and 198 with EGC. In EGC patients, en bloc resection was achieved in 89.7% (177/198), the complete resection rate was 87.9% (174/198), and the local recurrence rate was 5.1% (10/198). Tumor size >20 mm was significantly associated with local recurrence (odds ratio 6.45; 95% CI 1.20-20.11; p=0.001). There were significant correlations between the incidences of a piecemeal or incomplete resection and that of local recurrence (odds ratio 5.23; 95% CI 1.02-18.34; p=0.001; and odds ratio 6.99; 95% CI 1.22-21.65; p=0.002, respectively). The 3-year cancer-free survival rate was 94.9%. CONCLUSIONS. Curative treatment with successful en bloc resection can reduce the local recurrence of gastric neoplastic lesions after ESD. Clinical outcome may be excellent, although longer follow-up studies are warranted.