This case illustrates the clinical features of lithium intoxication and the problems in treating it that may arise as a result of lithium's effects on the kidney. It also demonstrates the difficulties that can develop when a delicate physiologic balance is inadvertently disrupted by nonpharmacologic interventions such as seclusion and consequent restriction of access to food and water. Patients with lithium-induced urine-concentrating defects are especially at risk for dehydration, and care must be taken to ensure adequate fluid and salt intake. This case also shows how intense negative feelings evoked by chronically mentally ill patients can adversely affect their psychiatric and medical care. While such feelings are inevitable, their impact may be lessened by improved communication and coordination between the medical and psychiatric systems of care and by the presence of psychiatrists in the general medical hospital.