The aim of this study was to demonstrate epidemiological, clinical and endoscopic characteristics of acute upper gastrointestinal bleeding (UGIB) with special reference to peptic ulcer bleeding (PUB). The study included 2198 consecutive patients referred to our emergency department due to acute UGIB from January 2008 to December 2012. All patients underwent urgent upper GI endoscopy within 24 hours of admission, and 842 patients diagnosed with PUB were enrolled and prospectively followed-up. The cumulative incidence of UGIB was 126/100,000 in the 5-year period. Two out of five patients had a bleeding peptic ulcer; in total, 440 (52.3%) had bleeding gastric ulcer, 356 (42.3%) had bleeding duodenal ulcer, 17 (2%) had both bleeding gastric and duodenal ulcers, and 29 (3.5%) patients had bleeding ulcers on gastroenteric anastomoses. PUB was more common in men. The mean patient age was 65.9 years. The majority of patients (57%) with PUB were taking agents that attenuate the cytoprotective function of gastric and duodenal mucosa. Rebleeding occurred in 77 (9.7%) patients and 47 (5.9%) patients required surgical intervention. The 30-day morality was 5.2% and 10% of patients died from uncontrolled bleeding and concomitant diseases. In conclusion, PUB is the main cause of UGIB, characterized by a significant rebleeding rate and mortality.