The development of life-threatening hyperkalemia poses a risk for patients with chronic preterminal renal failure. Various therapeutic options have been suggested for hyperkalemic emergencies in these patients; to date, however, no study has evaluated the relative efficacies of these measures in the presence of renal failure. Our goal was to examine the acute effects of a variety of therapeutic approaches, as well as those of hemodialysis, on plasma potassium levels in a hemodialysis population. Ten patients with terminal renal failure undergoing maintenance hemodialysis were enrolled in the study. Blood gas parameters and plasma sodium, potassium, glucose, osmolality, renin, aldosterone, epinephrine, norepinephrine, dopamine, and insulin were measured before, during, and after 60-minute infusions of bicarbonate, epinephrine, and insulin in glucose, and before, during, and after performance of regular hemodialysis for one hour. Hypertonic as well as isotonic intravenous bicarbonate (2 to 4 mmol/minute) induced a marked rise in plasma bicarbonate and pH, but failed to lower the plasma potassium level (5.66 versus 5.83 mmol/liter before and after). Epinephrine, 0.05 microgram/kg/minute administered intravenously, decreased plasma potassium only slightly from 5.57 to 5.25 mmol/liter, and five patients showed no decline. On the other hand, insulin in glucose, 5 mU/kg/minute intravenously, effectively lowered plasma potassium levels from 5.62 to 4.70 mmol/liter, and hemodialysis induced the most rapid decline from 5.63 to 4.29 mmol/liter. Plasma aldosterone was elevated before treatment; it correlated with plasma potassium and dropped during intravenous bicarbonate administration or hemodialysis. Pretreatment plasma renin activity, insulin, epinephrine, norepinephrine, and dopamine levels were generally normal. We conclude that in patients with terminal renal failure undergoing maintenance hemodialysis, intravenous bicarbonate is ineffective in lowering plasma potassium rapidly, and epinephrine is effective in only half the patients, whereas insulin in glucose is a fast and reliable form of therapy for hyperkalemic emergencies. Plasma aldosterone levels are appropriate in relationship to plasma potassium levels, and levels of other potassium-influencing hormones are generally normal.