The structural and electronic transport properties ofABO3-type compoundsLa2/3−xRxCa1/3MnO3(R=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, Er, and Tm) with a fixed tolerance factor oft=0.91137 is studied. Similar structure deformation, characterized by the nearly constant average Mn–O,A–O distances and Mn–O–Mn bond angles, is observed in different compounds. The metal–semiconductor transition shows a strongRdependent feature. The transition temperature decreases monotonously from 187 to 77.6 K asRvaries from Tm to Pr, with a corresponding maximum resistivity ranging from 2.34 to6.17×104 &OHgr; cm. Very different magnetoresistance effects are also observed in this series of compounds. By assuming the presence of inhomogeneous local lattice distortions due to ions with different sizes atAsites and their mismatch withBions, the lattice effects can be understood qualitatively. ©1997 American Institute of Physics.