Background and aim:H. pylori and nonsteroidal anti-inflammatory drugs (NSAIDs) remain the major causes of peptic ulcer disease. Nevertheless, non- H. pylori non-NSAIDs peptic ulcers or idiopathic peptic ulcer disease (IPUD) constitute a growing problem associated with many complications. Gastric cancer and gastrointestinal stromal tumor (GIST) have also been reported as a cause of IPUD. This study was aimed to investigate prevalence and clinical characteristics of IPUD in Thailand.Materials and Methods:Clinical information, histological features, endoscopic findings, history of H. pylori status and NSAIDs usage were collected for patients diagnosed with PUD in Thammasat University Hospital during January 2003 – December 2013.Results:Total of 1,310 patients was diagnosed with PUD in our institution during the study period, of which 71 (5.4%) had a definitive diagnosis of IPUD (45 men and 26 women, mean age of 59±16.5 years). Common locations were gastric antrum (43.7%), duodenum (25.3%) and gastric body (12.7%). Common causes of IPUD were idiopathic (43.7%) and alcohol consumption (39.4%). Gastric cancer and GIST were also demonstrated in 1(1.4%) and 1(1.4%) respectively. Major complications were upper GI bleeding (73.2%) and peptic perforation (2.8%). Recurrent upper GI bleeding was detected in 23.9%. Interestingly, male patients aged<50 years with alcohol related peptic ulcer were significantly more common than female patients aged ≥ 50 years (57.8% vs 7.7%;P-value= 0.00002, OR= 16.4, 95%CI= 3.5-78 and 68.4% vs 28.9%); P-value= 0.002, OR= 5.3, 95% CI= 1.7-16.7).Conclusion:Common causes of IPUD in Thailand are idiopathic followed by alcohol consumption and steroid usage. Gastric cancer and GIST are also possible causes of IPUD. These particular ulcers had a high likelihood of developing severe complications. Appropriate screening and high level of suspicion of fatal causes eg. gastric cancer and GIST should be appropriate ways to reduce complications and improve the treatment outcome.