1 Al-26 and Ga-67 were given as citrates to a healthy male volunteer by intravenous injection. The retention of both tracers was studied by body radioactivity measurement. Levels in blood and excreta were determined by gamma-ray spectrometry and/or accelerator mass spectrometry. 2 More than half of the Al-26 had left the blood after 15 min and the decline continued, leaving <1% in blood after 2 d; the losses occurred both to renal excretion and through uptake by other compartments. Estimated excretion up to 13 d was 83% (urine) and 1.8% (faeces). Whole-body retention of 15% at 13 d declined to similar to 4% at 1178 d, when the daily reduction corresponded to a biological half-life of 7 y, suggesting that sustained intake of dietary aluminium may lead to a progressively increasing internal deposit. 3 The metabolism of Ga-67 differed markedly from that of Al-26 in all aspects studied.