Symptomatic hypermagnesemia usually requires both increased intake of the ion and abnormal renal function; however, we treated two patients with iatrogenic hypermagnesemia (10.4 and 13.2 mEg/L) who had normal renal function. One received ureteral irrigation with hemiacidrin (Renacidin) to dissolve a stone, and the other was treated for ingestion of an unknown toxin with large doses of magnesium sulfate. Therapy included ventilatory support, intravenous calcium, and fluids. Dialysis was not required, and recovery was complete.