A hospitalized patient with renal failure receiving oral aluminium hydroxide was found to have a blood aluminium level of 3124 micrograms/l (116 mumol/l). 2. The extremely high aluminium concentration was attributed to the concurrent use of an oral citrate solution which converted the aluminium to a more soluble and absorbable form. 3. The combination of oral aluminium and citrate should be avoided in patients with poor renal function.