[en] Continuous administration of ⁶³NiCl₂ solution was performed in rats by ip implantation of osmotically driven minipumps. Renal ⁶³Ni clearance averaged 6.4 ml/hr during the interval from 24 to 96 hr after initiation of the infusion. During the infusion, plasma ⁶³Ni concentrations at 4:00 p.m. averaged 36% higher than those at 9:00 a.m., suggesting diurnal fluctuation of nickel metabolism in rats. Three chelating drugs were administered to groups of six rats by sc implantation of minipumps during simultaneous ip infusion of ⁶³NiCl₂, in order to compare the effectiveness of the drugs in enhancing renal ⁶³Ni excretion