Purpose: To clarify physician- and nurse-reported effects of intravenous hydration therapy on symptoms of terminally ill patients with cancer. Methods: A cross-sectional questionnaire survey of Japanese physicians and nurses. The respondents were requested to report their clinical observations about improvement or deterioration of seven symptoms of terminally ill patients with lung or gastric cancer receiving 0.5-1 L/d intravenous hydration therapy, 1.5-2 L/d intravenous hydration therapy, and reduction of intravenous hydration volume from 1.5-2 L/d to 0.5-1 L/d. Results: The responses from a total of 413 oncologists, 88 palliative care physicians, 2735 oncology nurses, and 593 palliative care nurses were analyzed (response rates, 53% in physicians and 83% in nurses). Fewer than 30% of the respondents in all specialties reported that they often or very often observed improvement of dehydration symptoms with 0.5-1 L/d or 1.5-2 L/d intravenous hydration therapy. Deterioration of fluid retention symptoms was reported by 5.8%-13% of the oncologists and 20%-50% of the other specialists with 0.5-1 L/d intravenous hydration therapy for patients with lung cancer, and by 9.3%-24% of the oncologists and 16%-68% of the other specialties with 1.5-2.0 L/d hydration for patients with gastric cancer. By reducing intravenous hydration volume, 20%-70% of the palliative care physicians and nurses reported that they often or very often observed improvement of fluid retention symptoms, while less than 7.0% of all specialists reported that they often or very often observed deterioration of dehydration symptoms. Conclusions: The physicians and nurses in both oncology and palliative care settings frequently observed deterioration of fluid retention symptoms with limited benefits in alleviating dehydration symptoms by intravenous hydration therapy for terminally ill patients with cancer. It is suggested that routine use of artificial hydration therapy should not be recommended, and individualized treatment policy based on the comprehensive assessment of each patient's needs is strongly required.