Here I attempted to analyze and summarize current data on etiology of duodenal ulcer, with the fo-cus on diagnostics and treatment of its perforation. Duodenal ulcer is diagnosed in ≈ 3% of the adult population worldwide, and 5-14% of the patients suffer from perforated ulcer. Duodenal ulcers are caused by a dysregulated balance between aggressive and protective factors of the intestinal mucosa. In up to 80% of the patients, it is caused by Helicobacter pylori infection; less commonly, it is associated with a long-term use of nonsteroidal anti-inflammatory drugs, excessive smoking, alcohol abuse, gastrinoma, starvation, emotional overload, and genetic disorders. Main clinical manifestations of perforated duodenal ulcer are sudden abdominal pain, symptoms of peritonitis, and tachycardia. In around 66% of patients, perforation symptoms are the first manifestations; in 60-91% of patients, pneumoperitoneum is diagnosed. Current diagnostic methods include ultrasound examination, computed tomography scan, duodenoscopy, laparoscopy and even laparocentesis. Treatment is based on laparotomic or laparoscopic suturing of the perforation. Vagotomy is considered a worthwhile addition, as it may prevent repeated ulceration. When perforated duodenal ulcers are combined with stenosis or bleeding, Judd pyloroplasty (diamond-shaped transverse excision) or Heineke-Mikulicz pyloroplasty (transversely closed longitudinal incision across the pylorus) is recommended. Sealing pads and endoscopic duodenal stenting may be considered as appropriate options in elderly patients with multiple comorbidities. Eradication therapy should be prescribed in patients with Helicobacter pylori infection. Late diagnosis, old age, severe or multiple comorbidities, and hypoalbuminemia are the risk factors of an adverse outcome; case fatality rate ranges from 0.3 to 30%. Overall, the number of perforated duodenal ulcers remains high.