This prospective study was undertaken to assess the state of hydration in terminal cancer patients with and without intravenous fluids during the last 48 hours of their lives and to correlate various measures of hydration with their state of consciousness. We examined indicators of hydration in the plasma and urine of 68 consecutive patients for whom data were available at 48 hours or less before death. Thirteen of the patients were being treated with intravenous (IV) fluids. Nearly all of the patients studied were found to be dehydrated, as determined by laboratory measurements. State of consciousness correlated inversely with serum sodium (p < 0.001) and urine osmolality (p < 0.02). Patients receiving intravenous fluids were not better hydrated than those without IV therapy, nor was their state of consciousness improved. In light of these findings, which suggest there is no clinical benefit from intravenous infusions, decisions regarding intravenous fluid therapy during the last hours of life should be guided by the preferences of the dying patient and his family.