Adrenal cysts are rare clinical and pathologic entities. The vast majority are minute in size, unilateral, and found in females at autopsy. They come to the physician's attention when they produce symptoms or are identified on x-ray studies. When symptomatic, they generally produce lumbar discomfort and gastrointestinal symptoms, and occasionally are palpable by abdominal examination. There is no significant agreement as to cause and pathogenesis of the disease. The most common histologic types are lymphangiomatous endothelial cysts, secondary to lymphangiectasis, and the fibrous wall or hemorrhagic pseudocysts. In many patients preoperative diagnosis is now possible with high quality nephrotomography, ultrasonography, and adrenal arteriography. The presence of a suprarenal mass with peripheral or laminar calcification strongly suggests the presence of an adrenal pseudocyst. Selective biochemical studies are mandatory to rule out the presence of an occult cystic pheochromocytoma, and adrenal cortical tumor. Adrenal cysts must be differentiated from all space-occupying lesions of the upper abdomen. Surgical exploration is recommended in almost all patients for accurate diagnosis and to rule out malignant disease or occult pheochromocytoma. The choice of the surgical approach should be planned to provide for safe and adequate exposure, depending on the size and location of the lesion. Careful dissection with preservation of the adjacent kidney, liver, and pancreas should be performed.