INTRODUCTION: Cases of localized and diffuse peritonitis are severe surgical conditions. Despite expanding possibilities for the diagnosis and therapy, patients with peritonitis, its diffuse form in particular, still suffer from high morbidity and mortality. The management of this condition, both in the healthy and especially seriously ill population, is not satisfactory. Recently, we have witnessed an increase in bariatric and metabolic surgery in response to an ever rising number of extremely obese patients worldwide. Bariatric patients belong to a group of seriously ill patients with a significant risk of post-operative complications due to an infection. Although their treatment is identical to that of the normal population, a great emphasis is put on early recognition of complications, and the decision on any potential surgical revision should be actively approached, often necessitating the absence of frequently lengthy paraclinical assessments. METHODS: We conducted a retrospective analysis of 346 obese bariatric patients undergoing surgical treatment for morbid obesity between August 2011 and August 2015. RESULTS: A total of 6 patients experienced severe complications including two cases of diffuse peritonitis, two cases of localized peritonitis and two cases of intraperitoneal bleeding. One patient died after her discharge from hospital due to toxic shock caused by stomach perforation. We describe two case reports in greater detail to highlight the importance of early detection of complications and a timely surgical intervention. CONCLUSION: In principle, bariatric patients are a severely ill population where standard diagnostic procedures for post-operative complications often fail. Clinical findings and the surgeons experience are commonly the only diagnostic signs that trigger a surgical revision. In contrast, surgical treatment of post-operative complications in obese patients with peritonitis is virtually identical to that in patients with normal or slightly increased BMI. It involves thorough toilette of the abdominal cavity, lavage and drainage. Due to high morbidity and large peritoneal surface, obese patients may deteriorate rapidly. Timely surgical intervention is thus the only proper therapeutic approach, even without any, often lengthy paraclinical assessments. KEY WORDS: peritonitis - bariatric surgery - complications in bariatric surgery.