Hyperosmolar hyperglycemic nonketotic coma is a serious and often lethal clinical biochemical syndrome. We report three cases of ophthalmic problems that were treated with a short course of oral corticosteroids and which resulted in the development of hyperosmolar hyperglycemic nonketotic coma. Two of these cases concerned relatively young, previously healthy patients and had fatal outcomes. The third patient, who was elderly, survived because of early detection and initiation of therapy. All three cases demonstrate that hyperosmolar hyperglycemic nonketotic coma is a serious potential complication of systemic steroidal therapy, even in a short course of treatment such as is often used in ophthalmology.