Background: Sarcina ventriculi, a gram-positive coccus, are occasionally found in gastric biopsies. Although Sarcina had been described more than 150 years ago, little is known about its pathogenicity in humans. Method: This retrospective case series included patients who were identified with Sarcina infection. We report clinicopathologic characteristics of 13 patients with Sarcina in gastric or duodenal biopsies. Result: The presenting symptoms included: epigastric discomfort (n=6), epigastric pain (n=4), anorexia (n=6), nausea and vomiting (n=5), constipation (n=2), diarrhoea (n=2) and weight loss (n=3). All patients had evidence of mucosal injury. Sarcina was found on mucosal surface.12 patients had food residue on oesophagogastroduodenoscopy (OGD). 10 patients had gastric outlet obstruction (GOO), antral narrowing in 7 and duodenal obstruction in 3. 6 patients had malignant GOO. Causes of benign GOO included Helicobacter Pylorigastritis (n=1), eosinophilic gastritis (n=1) and duodenal ulcers (n=2, 1 NSAIDs). Of the 5 patients that had follow-up OGD, 2 had gastric residue. One patient had recurrence of symptoms with the persistence of sarcina on biopsy at 3 months. Symptoms improved at 6 months and no evidence of sarcina on biopsy at 6 months. Conclusion: Our findings suggest GOOcan be considered as a predisposing factor for Sarcina infection. Sarcina infection may not be the aetiology for GOObut may complicate recovery and may lead to life-threatening complications. Clinicians and pathologists must be aware of such microorganisms and must be documented in the histology report for further investigation and therapeutic consideration.