[en] Kinetics of the substitution reactions of lanthanum(III), neodymium(III), samarium(III), gadolinium(III) and holmium(III) complexes of ethylenediaminetetraacetate(edta), N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetate(edtaoh) and 1,2-cyclohexanediamine-N,N,N',N'-tetraacetate(cydta) with lead(II) ions has been studied in the pH range of 2.38 -- 5.97, at an ionic strength of 0.1, in the presence of excess metal ions over a temperature range of 15 -- 30⁰C. The initial rate equations and activation parameters have been obtained from the measurement of change in absorbance in a region of 240 -- 245 nm by stopped-flow method. Observed rate constants are in the order: La>Nd>Sm>Gd>Ho for the edta and cydta systems, and La>Nd asymptotically equals Sm asymptotically equals Gd asymptotically equals Ho for the edtaoh system. The order of the effect of the ligands on the rate is edtaoh>edta>cydta for holmium and edta>edtaoh>cydta for the other metals. The rate constants for the formation of MHX sup((n-4)-) where M denotes the rare earth metal(III) and X sup(n-) a completely deprotonated ligand anion, are in the order of La< Nd< Sm>Gd< Ho and are lower than those expected from the Eigen-Tamm mechanism. (author)