A 54-year-old woman underwent colonoscopy for colon cancer screening. Colonoscopy showed multiple cysts in the sigmoid colon, with the largest being 4 cm in diameter. One of the cysts was biopsied. Cyst walls were observed; during biopsy, the gas was released and the cyst collapsed. Computed tomography of the abdomen confirmed a diagnosis of pneumatosis cystoides intestinalis. Pneumatosis cystoides intestinalis is a rare disease characterized by the presence in the intestinal submucosa or subserosa of multiple cysts filled with gas (nitrogen, oxygen, carbon dioxide and hydrogen). This condition occurs more often in males than in females, with cysts most frequently located in the colon. Causes may include elevated intraluminal pressure, pulmonary diseases, bacterial gas production, malnutrition, chemotherapy, connective tissue diseases, among others. Symptoms of pneumatosis cystoides intestinalis include abdominal pain, diarrhea, bloating and gastrointestinal bleeding. This condition is diagnosed by endoscopy or computed tomography of the abdomen. Conservative treatment is successful in 93% of patients. However, 3% of patients develop complications such as intestinal obstruction or perforation.