Duodenal ulcer has decreased in prevalence and incidence over the last 70years but remains a common condition complicated, most commonly, by bleeding and perforation. The principal risk factors for duodenal ulceration are gastric Helicobacter pylori infection and nonsteroidal antiinflammatory drugs (NSAID) although about one fifth of ulcers are attributable to other factors. Duodenal ulcer presents, typically, with dyspepsia but patients presenting with complications may not have experienced typical antecedent symptoms. Upper endoscopy is the investigation of choice for diagnosis, treatment of bleeding and mucosal biopsy to identify features of H. pylori infection, NSAID ingestion or other etiologies. Therapy is based on acid suppression with proton pump inhibitors (PPI) in conjunction, when possible, with treatment of the underlying cause including H. pylori eradication therapy and cessation of NSAID therapy; patients with persistent or recurrent duodenal ulcer despite these strategies may require long-term PPI therapy. H. pylori eradication therapy continues to evolve as antibiotic resistance becomes more prevalent; current guidelines recommend treatment for 2weeks, initially with a PPI-based regimen that includes three additional antibacterial agents. Confirmation of eradication requires a test of active infection such as a urea breath test, stool antigen test or upper endoscopy.