The need to treat dehydration in terminally ill patients has become a very controversial topic. Numerous reports in the literature illustrate opposing view-points from both clinical and ethical perspectives. Arguments for the maintenance of hydration in terminally ill patients have tended to come from "the traditional medical model". Many health care professionals looking after terminally ill patients have reacted to the generalized use of intravenous fluids in dying patients and the perceived negative effects of this management. Our palliative care group has argued that the viewpoint that dehydration in dying patients is not a cause of symptom distress overlooks commonly reported problems, such as agitated delirium, that can be prevented or reversed by the management of dehydration. This review presents a summary of the traditional arguments, a different perspective on the controversy, biochemical parameters reported in terminally ill cancer patients, recent dehydration research, and the use of hypodermoclysis and rectal hydration. We conclude that the data reported to date are insufficient to allow a final conclusion on the benefit or harm of dehydration in terminally ill patients. Nevertheless, it is worth considering that while some dying patients may not suffer any ill effects from dehydration, there may be others who do manifest symptoms, such as confusion or opioid toxicity, that might be alleviated or prevented by parenteral hydration.