Mesenteric cysts are extremely rare abdominal tumors. Approximately two thirds of patients with these tumors are aduls. Most of the cases are either asymptomatic or present themselves with non-specific abdominal symptoms. Less common, these tumors may grow to enormous proportions, present with features of bowel compression. A giant sigmoid mesenteric cyst, surgically removed in a 78-year-old woman is described. Also the clinical, diagnostic, and treatment aspects of mesenteric cysts are briefly discussed.