A series of iron perovskites with the general formula AFeO(3-delta) (A=Ln(1-x)M(x::)Ln=La, Nd and/or Pr; M=Sr and/or Ca) has been prepared by conventional solid state reaction. In order to isolate the effect of divalent doparn concentration from the A cation steric effects, the whole group has a fixed mean A cation radius approximate to 1.22 angstrom and cation size disorder sigma(2) (r(A)) approximate to 0.003 angstrom(2) but variable doping x. The structure changes with x from orthorhombie (0.2 <= x <= 0.4) through rhombohedral (0.5 <= x <= 0.7) to a mixture of rhombohedral and cubic for x=0.8. SEM images show that the average grain size increases with alkaline-earth content. All samples show a systematic dependence of conductivity upon doping, which can be directly related to the concentration of charge carriers. Conductivity fits indicate a p-type semiconducting, small-polaron hopping mechanism, in which the activation energies remain similar for all doping levels, x, throughout the series. (C) 2007 Elsevier B.V. All rights reserved.