A distinctive symptom pattern was observed during theaccidental, simultaneous occurrence of severe hypernatremia in 6 hemodialysis patients. Thirst, hot flushes, headache, nausea and vomiting, weakness and disorientation accurred in all cases in a similar sequence. Low back and abdominal pain, severe dyspnea and hypoacusia followed in one third of the cases. The highest serum sodium concentration was 165 mEq/l. Extracellular volume changes were minimal, as well as blood pressure increases. Weight gains were accounted for by intracellular water expansion during rehydration. No neurological complications or deaths resulted.