Objectives: Peptic ulcer perforation (PUP) accounts for 5% of all abdominal emergencies and is recognized as a gastrointestinal emergency requiring rapid and efficient clinical evaluation and treatment. The mortality rate ranges from 10% to 40% among patients with perforation. In the present retrospective study, we examined the potential utility of the neutrophil-to-lymphocyte ratio (NLR) in early diagnosis of PUP; we asked whether this ratio allowed PUP and peptic ulcer disease to be distinguished.