Pneumatosis cystoides intestinalis (PCI) with associated eosinophilic inflammation was documented in the gastric tissues of four black and white ruffed lemurs (Varecia variegata variegata). Pneumatosis cystoides intestinalis is an uncommon disease described in humans and characterized by multilocular gas-filled cystic spaces located within the wall of the gastrointestinal tract. These cystic spaces can occur in any location along the gastrointestinal tract as well as within the associated connective and lymphatic tissues. The exact cause of this disease is unknown. The four black and white ruffed lemurs described in this case series were captive born and had been housed in zoological institutions at two separate locations. Three of the four cases were female lemurs, and two of the affected lemurs were directly related. The individual disease presentations spanned a 5-yr time period. Two lemurs presented dead with no premonitory signs, whereas the other two lemurs presented with clinical signs of gastrointestinal disease and nonspecific signs of weakness. Gastric pneumatosis, diagnosed either grossly or histopathologically in each of these four lemurs, is described as a subset of PCI in which cystic spaces are localized to the stomach wall. Significant eosinophilic inflammatory infiltrate was identified on histopathology of gastric tissues and found to be associated with the cystic lesions in each lemur. No classic etiology, such as a fungal infection or a parasitic infection, was identified as the cause of the eosinophilic gastritis. This case series demonstrates that gastric pneumatosis with associated eosinophilic gastritis may be a significant gastrointestinal disease in black and white ruffed lemurs.